LIBRARY 

OF  THE 

UNIVERSITY  OF  CALIFORNIA. 


Class 


ELECTRIC    RAILWAYS 


A  Series    of    Papers  and  Discus- 
sions   Presented    at   the    Interna- 

** 

tional    Electrical  Congress  in  St. 
Louis,    1904 


REPUBLISHETBY  THE 

McGRAW  PUBLISHING  COMPANY 

NEW  YORK 

By  Special  Arrangement  w:th  the 
International     Electrical    Congress 

1907 


A 

•&. 


COPYRIGHTED,  1906 

by  the 

McGRAW  PUBLISHING  COMPANY 
New  York 


PREFACE. 


The  papers  and  discussions  here  reprinted  define  the  state 
of  the  art  of  electric  traction  at  the  epoch  of  the  St.  Louis 
Exposition.  The  Electrical  Congress  of  1904  was  in  all  respects 
valuable,  but  the  papers  on  electric  traction  are  particularly 
important,  as  marking  the  beginning  of  a  new  era  —  that  of 
heavy  railway  work,  with  the  introduction  of  single  phase 
alternating  motors.  The  valuable  papers  of  Arnold,  Dawson, 
Steinmetz,  Deri,  and  others  represent  the  new  point  of  view 
which  entirely  changes  the  aspect  of  electric  railway  operation. 
For  the  previous  decade  the  methods  of  electric  traction  had 
remained  essentially  unchanged.  They  had  been  stretched  be- 
yond the  elastic  limit,  so  to  speak,  in  the  endeavor  to  reach 
expanding  conditions,  and  the  logic  of  events  demanded  a 
change.  The  realization  of  this  was  strongly  in  evidence  at  the 
Congress  of  1904,  and  the  developments  of  the  two  years  since 
passed  have  been  directly  along  the  lines  then  plainly  foreseen. 
In  fact,  with  few  exceptions,  the  papers  here  presented  bear  the 
prophetic  impress,  and  while  the  older  methods  found  some 
vigorous  support,  the  handwriting  on  the  wall  was  plain  for  all 
to  read.  Achievement  follows  foresight,  and  commercial  adapt- 
ation trails  in  the  rear,  so  that  one  need  not  wonder  at  the  ap- 
parently gradual  progress  in  the  actual  equipment  of  roads. 
Such  has  been  the  history  of  other  improvements,  of  the  appli- 
cation of  alternating  currents  to  lighting  and  of  polyphase  cur- 


1B1539 


iv  PREFACE. 

I 

rents  to  the  electrical  transmission  of  power.  But  methods  in- 
evitably change  with  the  times,  and  one  reading  these  papers 
half  a  dozen  years  hence  will  marvel,  not  so  much  at  the  insight 
of  the  engineers  who  wrote  them,  as  that  the  work  had  already 
been  so  long  delayed.  Progress  seems  easy  when  viewed  from 
a  sufficient  distance.  This  volume  records  the  field  notes  of 

the  advance  guard. 

LOUIS  BELL. 
BOSTON,  MASS. 


CONTENTS. 


Page, 
The  history  and  development  of  electric  railways 1 

Some  early  work  in  polyphase  and  single-phase  electric  traction 21 

Electric  traction  on  British  railways 52 

The  Monorail   railway 76 

The  electrification  of  steam    railroads    83 

Alternating  vs.  Direct-current  traction   • Ill 

Notes  on  equipment  of  the  Wilkesbarre  &  Hazelton  railway 189 

Transmission  and  distributing   problems  peculiar   to  the  single-phase 

railway   230 

Protection  and  control   of  large  high-tension  alternating-current  dis- 
tribution systems 238 

Rotary  converters  and  motor-generator  sets 252 

The  Booster  machine  in  traction  service    and  its  proper  regulation...  262 

Storage  batteries  in  electric  railway  service 275 

Electrolysis  of  underground  conductors 288 

Braking   high-speed  trains    315 

Alternating-current  motors   323 

Single-phase  motors    376 

Alternating-current  machines  with  gramme  commutators 396 

Single-phases  railway  motors  402 

Theory  and  operation  of  the  repulsion  motor , 410 

Theory  of  the  compensated  repulsion  motor 429 


ELECTRIC  POWER  TRANSMISSION  COMMITTEE 

1904 

Honorary  Chairman,  M.  PAUL  JANET  AND  ING.  A.  MAFFEZINI. 

Chairman,  MR.  CHAS.  F.  SCOTT. 

Vice-President,   ING.    E.   JONA. 

Secretary,  DR.  LOUIS  BELL. 


OF  THE  A 

UNIVERSITY    ) 

°F 


THE  HISTORY  AND  DEVELOPMENT  OF  ELEC- 
TRIC RAILWAYS. 

BY  FRANK  J.  SPRAGUE. 


Although  the  earliest  recorded  experiments  date  back  three-quar- 
ters of  a  century,  the  electric  railway  is  essentially  of  modern  de- 
velopment, for  it  achieved  a  recognized  position  less  than  twenty 
years  ago,  long  after  the  telephone,  the  arc  and  incandescent  lamp, 
and  the  -stationary  electric  motor  had  been  thoroughly  established. 
This  is  but  natural,  for  it  is  the  logical  outcome  of  the  establish- 
ment of  certain  cardinal  principles  and  practices  in  the  kindred 
arts. 

The  first  roads  to  carry  passengers  commercially  were  built  in 
Europe,  but  the  first  railway  experiments  and  the  modern  com- 
mercial impetus,  as  well  as  most  of  the  essential  and  distinctive 
features  of  the  art  as  it  stands  today,  an  example  of  almost  unpre- 
cedented industrial  development,  are  distinctively  American. 

Brandon,  Vt.,  birthplace,  and  Thomas  Davenport,  blacksmith, 
father,  are  the  names  first  on  the  genealogical  tree  of  the  electric 
railway,  in  the  year  1834.  A  toy  motor  mounted  on  wheels,  pro- 
pelled on  a  few  feet  of  circular  railway  by  a  primary  battery,  ex- 
hibited a  year  later  at  Springfield,  and  again  at  Boston,  in  the 
infant's  photograph.  This  was  only  three  years  after  Henry's  in- 
vention of  the  motor,  following  Faraday's  discovery  ten  yearn 
earlier  that  electricity  could  be  used  to  produce  continuous  motion. 

The  records  of  Davenport's  career,  unearthed  by  the  late  Franklir* 
Leonard  Pope,  show  this  early  inventor  a  man  of  genius  deserving 
a  high  place  in  the  niche  of  fame,  for  in  a  period  of  six  years  he 
built  more  than  a  hundred  operative  electric  motors  of  various 

NOTE  — The  writer  having  been  requested  to  prepare  a  paper  on  the  sub- 
ject of  electric  railways  has  done  so  with  considerable  reluctance  because  of  his 
own  connection  with  the  art,  and  the  difficulty  under  such  circumstances  in 
presenting  events  in  a  true  perspective,  unbiased  by  personal  experiences. 
That  such  must  be  spoken  of  is,  while  embarassing,  somewhat  necessary,  and 
due  allowances  should  be  made  in  his  estimate  of  their  importance. 

ELEC.  BYS. —  1.  [1] 


Z  8PRAGUE:     ELECTRIC  RAILWAYS. 

designs,  many  of  which  were  put  into  actual  service,  an  achieve- 
ment, taking  into  account  the  times,  well  nigh  incredible. 

For  nearly  two  score  years  various  inventors,  handicapped  with 
the  limitations  of  the  primary  battery,  and  in  utter  ignorance  of 
the  principles  of  modern  dynamo  and  motor  construction,  labored 
with  small  result.  About  1838,  a  Scotchman,  Robert  Davidson  of 
Aberdeen,  began  the  construction  of  a  locomotive  driven  by  a  motor 
similar  to  that  used  by  Jacobi  in  his  experiments  on  the  river 
Keva,  which  was  tried  upon  the  Edinboro-Glasgow  Railway,  and 
attained  a  speed  of  about  four  miles  an  hour. 

In  an  English  patent  issued  to  Henry  Pinkus  in  1840,  the  use 
of  the  rails  for  currents  was  indicated;  also  in  a  United  States 
patent  issued  to  Lilley  and  Colton  of  Pittsburg  in  1847. 

In  1847,  Prof.  Moses  G.  Farmer,  late  United  States  govern- 
ment electrician  at  the  Newport  Station,  one  of  the  most  learned 
and  able  of  the  early  electric  experimenters,  operated  an  experi- 
mental model  car  at  Dover,  N.  H. ;  and  about  three  years  later  one 
Thomas  Hall  exhibited  in  Boston  an  automatically  reversing  car 
mounted  on  rails  through  which  current  was  supplied  from  M 
battery.  These  are  said  to  be  the  first  instances  in  which  rails  were: 
actually  used  as  carriers  of  the  current,  as  well  as  the  first  time 
where  there  was  a  reduction  by  gear  from  the  higher  speed  on  the 
motor  to  the  lower  speed  of  the  driven  axle. 

About  the  same  time  Prof.  Paga  of  the  Smithsonian  In- 
stitute, aided  by  a  special  grant  from  Congress,  constructed  a 
locomotive  in  which  he  used  a  double  solenoid  motor  with  recipro- 
cating plunger  and  fly-wheel,  as  well  as  some  other  forms.  This 
locomotive,  driven  by  a  battery  of  100  Grove  elements,  was  tried 
the  29th  of  April,  1851,  upon  a  railroad  running  from  Washington 
to  Bladensburg,  and  attained  a  fair  rate  of  speed. 

Patents  issued  in  1855  to  an  Englishman  named  Swear  and  a 
Piemontais  named  Bessolo  indicated  the  possibility  of  collecting 
current  from  a  conductor  suspended  above  the  ground,  and  in  1864 
a  Frenchman  named  Cazal  patented  the  application  of  an  electric 
motor  to  the  axle  of  the  vehicle. 

From  the  experiments  of  Farmer  and  Hall  a  decade  elapsed  be- 
fore the  invention  by  Pacinotti  in  1861  of  the  continuous  current 
dynamo,  from  which  may  properly  be  said  to  date  all  modern  elec- 
tric machines.  These  were  developed  in  their  earliest  forms  by 
Gramme  and  Siemens,  Wheatstone  and  Varley,  Farmer  and  Row- 


8PRACUE:     ELECTRIC  RAILWAYS. 

land,  Hefner- Alteneck  and  others,  and  brought  into  existence  the 
elements  essential  to  any  possible  commercial  success.  Yet  not- 
withstanding that  the  principle  of  the  reversibility  of  the  dynamo- 
electric  machine,  and  the  transmission  of  energy  to  a  distance  by 
the  use  of  two  similar  machines,  said  to  have  been  discovered  and 
described  by  Pacinotti  in  1867  —  the  same  year  in  which  Prof. 
Farmer  described  the  principle  of  the  modern  dynamo  in  a  letter 
to  Henry  Wilde  —  and  demonstrated  independently  at  the  Vienna 
Exposition  by  Fontaine  and  Gramme  in  1873,  many  years  more 
passed  before  the  importance  and  availability  of  this  principle  were 
generally  recognized. 

From  1850  to  1875,  is  a  long  period,  relatively,  and  yet  there 
seemed  to  have  been  practically  an  entire  cessation  of  experimental 
electric  railway  work,  until  in  the  latter  year  George  F.  Greene,  a 
poor  mechanic  of  Kalamazoo,  Mich.,  built  a  small  model  motor 
which  was  supplied  from  a  battery  through  an  overhead  line,  with 
track  return,  and  three  years  later  he  constructed  another  model 
on  a  larger  scale.  Greene  seemed  to  have  realized  that  a  dynamo 
was  essential  to  success,  but  he  did  not  know  how  to  make  one,  and 
did  not  have  the  means  to  buy  it. 

Shortly  afterward,  in  1879,  at  the  Berlin  Exposition,  Messrs. 
Siemens  and  Halske  constructed  a  short  line  about  a  third  of  a 
mile  in  length,  which^  was  the  beginning  of  much  active  work  by 
this  firm.  The  dynamo  and  motor  were  of  the  now  well-known 
Siemens  type,  and  the  current  was  supplied  through  a  central  rail, 
with  the  running  rails  as  a  return,  to  a  small  locomotive  on  which 
the  motor  was  carried  longitudinally,  motion  being  transmitted 
through  spur  and  beveled  gears  to  a  central  shaft  from  which 
connection  was  made  to  the  wheels.  The  locomotive  drew  three 
small  cars  having  a  capacity  of  about  20  people,  and  attained  the 
speed  of  about  eight  miles  an  hour. 

In  the  same  year  important  experiments  were  carried  on  by 
Messrs.  Felix  and  Chretien  at  the  little  village  of  Sermaize  in 
France  to  demonstrate  the  possibilities  of  the  transmission  of 
energy. 

At  Vienna  in  the  following  year,  Egger  exhibited  a  model  of  an 
electric  railway,  the  current  to  be  supplied  through  the  running 
rails.  About  the  same  time  Messrs.  Bontemps  and  Desprez  made 
a  study  of  a  scheme  for  replacing  pneumatic  transmission  of  dis- 
patches by  miniature  electric  locomotives  in  Paris. 


4  SPRAQUE:     ELECTRIC  RAILWAYS. 

The  Siemens  and  Halske  demonstration  in  Berlin  was  followed 
by  others  for  exhibition  purposes  at  Brussels,  Dusseldorf  and  Frank- 
fort, but  no  regular  line  was  established  until  a  short  one  with 
one  motor  car  at  Lichterfelde,  near  Berlin,  the  first  in  Europe,  or 
in  fact  in  the  world.  This  road  was  1  1/2  miles  in  length,  used 
all  rail  conductors,  and  was  opened  for  traffic  in  May,  1881. 

The  motor  was  carried  on  a  frame  underneath  the  car  between 
the  wheels,  and  current  transmitted  from  the  armature  to  drums 
on  the  axles  by  steel  cables.  The  car  was  of  fair  size,  having  a 
capacity  of  36  passengers,  and  attained  a  maximum  speed  of  about 
30  miles.  The  e.m.f.  used  was  about  100  volts.  This  line  was  con- 
tinued in  regular  service,  but  12  years  later  the  rail  method  of  dis- 
tribution was  replaced  by  two  conductors  carried  on  top  of  poles, 
upon  which  ran  a  small  carriage  connected  to  the  gear  by  a  flexible 
cable. 

Shortly  afterward  the  same  firm  installed  at  the  Paris  Electrical 
Exposition  of  1881,  a  small  tramway  about  a  third  of  a  mile  long, 
and  used  for  the  first  time  overhead  distribution.  In  this  case  the 
conductors  consisted  of  two  tubes  slotted  on  the  under  side,  and  sup- 
ported by  wooden  insulators.  In  the  tubes  slid  shoes  which  were 
held  in  good  contact  by  an  underrunning  wheel  pressed  up  by 
springs  carried  on  a  frame-work  supported  by  the  conductors,  and 
connected  to  the  car  by  flexible  conductors.  The  motor  was  placed 
between  the  wheels,  and  the  power  was  transmitted  by  a  chain. 

About  the  same  time  Siemens  constructed  an  experimental  road 
near  Meran  in  the  Tyrol  with  a  view  of  demonstrating  the  possibili- 
ties of  electric  traction  for  the  San  Gothard  tunnel,  and  later  other 
small  lines  at  Frankfort,  Molding  and  elsewhere.  These  were  fol- 
lowed by  a  comprehensive  scheme  for  a  combined  elevated  and 
underground  road  submitted  to  the  city  authorities  at  Vienna. 

The  invention  about  this  time  of  accumulators  directed  attention 
to  the  possibilities  of  the  self-contained  car,  and  in  1880  a  loco- 
motive with  accumulators  was  used  at  the  establishment  of  Du- 
•chesne-Fournet  at  Breuil,  and  in  the  following  year  Kaffard  with 
a  large  battery  of  Faure  accumulators  made  experiments  on  the 
tramway  at  Vincennes. 

In  1881,  Dr.  John  Hopkinson,  in  describing  the  application  of 
motors  to  hoists,  proposed  both  for  them  and  for  tramways  the 
simple  series-parallel  control  for  speed,  a  principle  which  combined 
vdth  resistance  variation  later  became  universal. 


SPRAGUE:    ELECTRIC  RAILWAYS.  5 

Meanwhile  in  the  United  States  two  inventors,  Stephen  D.  Field 
and  Thomas  A.  Edison,  began  electric  experiments  almost  simul- 
taneously. Edison  was  perhaps  nearer  than  any  other  on  the 
verge  of  great  possibilities  had  it  not  been  that  he  was  intensely 
absorbed  in  the  development  of  the  electric  light,  for  he  had  in  the 
face  of  much  adverse  criticism  developed  the  essentials  of  the  low 
internal  resistance  dynamo  with  high-resistance  field,  and  many  of 
the  essential  features  of  the  multiple  arc  system  of  distribution. 
In  fact,  in  1880  he  built  a  small  road  at  his  laboratory  at  Menlo 
Park,  on  which  he  ran  a  car  operated  by  one  of  his  earliest  dynamos 
from  which  the  power  was  transmftted  to  the  axle  by  a  belt.  One 
set  of  wheels  was  insulated,  and  the  two  rails  were  used  for  current. 
But  beyond  taking  out  a  few  patents,  and  for  a  while  acting  in 
conjunction  with  Field,  Edison  did  little  in  this  particular  field, 
and  soon  ceased  to  be  a  factor. 

Perhaps  more  than  to  any  other  the  credit  for  the  first  serious 
proposal  in  the  United  States  should  be  awarded  to  Field.  Curi- 
ously enough,  patent  papers  were  filed  by  Field,  Siemens  and 
Edison,  all  within  three  months  of  each  other  in  the  spring  and 
summer  of  1880.  Priority  of  invention  was  finally  awarded  to 
Field,  he  having  filed  a  caveat  a  year  before.  He  had  been  actively 
interested  in  electric  telegraphs,  and  in  an  account  of  his  work  pub- 
lished some  20  years  ago,  it  is  stated  that  he  early  constructed  two 
electric  motors,  and  had  in  mind  the  operation  of  street  cars  in 
San  Francisco,  but  had  not  been  able  to  do  anything  in  the  matter 
because1  of  a  realization  that  a  dynamo  must  be  used  instead  of  a 
battery.  In  1877  while  in  Europe  he  saw  some  Gramme  machines, 
and  on  his  return  two  of  them  were  ordered  but  not  delivered. 
Later  a  dynamo  was  ordered  from  Siemens  Brothers  in  London 
which  was  lost,  and  this  was  replaced  by  another  which  arrived 
in  the  fall  of  1878.  Meanwhile  two  Gramme  machines  were  placed 
at  his  disposal,  and  shortly  afterward  an  electric  elevator  was 
operated.  In  February,  1879,  he  made  plans  for  an  electric  rail- 
way, the  current  to  be  delivered  from  a  stationary  source  of  power 
through  a  wire  enclosed  in  a  conduit,  with  rail  return,  and  in 
1880-81,  he  constructed  and  put  in  operation  an  experimental 
electric  locomotive  in  Stockbridge,  Mass. 

Pending  the  settlement  of  patent  interferences  between  Edison 
and  Field  (the  Siemens  application  being  late  was  rejected),  the 
two  interests  were  combined  in  a  corporation  known  as  "  The  Elec- 
tric Railway  Company  of  the  United  States,"  and  the  first  work  of 


6  8PRAGUE:     ELECTRIC  RAILWAYS. 

the  company  was  the  operation  of  an  electric  locomotive  at  the 
Chicago  Eailway  Exposition  in  1883.  This  locomotive  called  "The 
Judge,57  after  the  late  Chief  Justice  Field,  ran  around  the  gallery 
of  the  main  exposition  building  on  a  track  of  about  one-third  of  a 
mile  in  length.  The  motor  used  was  a  Weston  dynamo  mounted 
on  the  car  and  connected  by  beveled  gear  to  a  shaft  from  which 
power  was  transmitted  by  belts  to  one  of  the  wheels.  The  current 
was  taken  from  a  center  rail,  with  track  return.  A  lever  operated 
clutches  on  the  driving  shaft,  and  the  speed  was  varied  by  re- 
sistance. The  reversing  mechanism  consisted  of  two  movable 
brushholder  arms  geared  to  a  cfisk  operated  by  a  lever,  each  arm 
carrying  a  pair  of  brushes  one  of  which  only  could  be  thown  into 
circuit  at  a  time,  to  give  the  proper  direction  of  movement. 

Meanwhile  several  other  inventors  were  getting  actively  into  the 
field  of  transmission  of  power  and  electric  railways.  In  the  sum- 
mer of  1882,  Dr.  Joseph  E.  Finney  operated  in  Allegheny,  Pa.,  a 
car  for  which  current  was  supplied  through  an  overhead  wire  on 
which  traveled  a  small  trolley  connected  to  the  car  with  a  flexible 
cable,  and  about  the  same  time  in  England  Dr.  Fleming  Jenkin, 
following  a  paper  by  Messrs.  Ayrton  and  Perry  before  the  Royal 
Institution  on  an  automatic  railway,  proposed  a  scheme  of  telpher- 
age which  was  developed  by  those  gentlemen. 

In  the  early  part  of  the  same  year,  the  writer,  then  a  midship- 
man in  the  United  States  Navy,  who  had  in  1879  and  1880  begun 
the  designing  of  motors,  was  ordered  on  duty  at  the  Crystal  Palace 
Electrical  Exhibition,  then  being  held  at  Sydenham,  England. 
While  in  London  he  became  impressed  with  a  belief  in  the  pos- 
sibility of  operating  the  underground  railway  electrically.  He  first 
considered  the  use  of  main  and  working  conductors,  the  latter 
being  carried  between  the  tracks,  with  rail  return,  but  noting  the 
complication  of  switches  on  certain  sections  of  the  road,  conceived 
the  idea  of  a  car  moving  between  two  planes,  traveling  on  one 
and  making  upper  pressure  contact  with  the  other,  those  planes 
being  the  terminals  of  a  constant  potential  system.  For  practical 
application  the  lower  of  the  two  planes  was  to  be  replaced  by  the 
running  track  and  all  switches  and  sidings,  and  the  upper  plane  by 
rigid  conductors  supported  by  the  roof  of  the  tunnel,  and  following 
the  center  lines  of  all  tracks  and  switches,  contact  to  be  made  there- 
with by  a  self-adjusting  device  carried  on  the  car  roof  over  the 
center  of  the  truck  and  pressed  upward  by  springs. 


SPRAGUE:     ELECTRIC  RAILWAYS.  7 

In  1882  he  applied  for  a  patent  on  the  first  idea,  which  was  but 
a  variation  from  that  shown  in  other  patents,  but  the  second  laid 
dormant  for  nearly  three  years  because  of  central  station  work  and 
the  development  of  the  application  of  stationary  motors. 

The  storage  battery  still  attracted  attention,  and  in  1883  experi- 
ments were  carried  on  at  Kew  Bridge,  London.  In  the  latter  part 
cf  1884  the  Electrical  Power  &  Storage  Company  of  London,  under 
the  direction  of  Anthony  Keckenzaun,  began  a  number  of  trials. 
The  same  engineer  repeated  his  work  at  Mill  Wall,  and  later  in 
Berlin.  The  car  body  in  his  last  experiment  was  carried  by  two 
trucks,  each  of  which  was  equipped  with  a  motor  driving  one  axle 
through  a  worm  gear.  Keversal  was  accomplished  by  using  two 
sets  of  brushes,  and  speed  was  varied  by  using  one  or  both  motors, 
also  by  using  the  motors  in  series  or  parallel  with  a  resistance  to 
cut  down  sparking  when  making  the  change  over. 

Reckenzaun  subsequently  had  charge  of  the  experiments  conducted 
by  Wm.  Wharton  of  Philadelphia,  in  which  both  a  Reckenzaun  and 
a  Sprague  motor  were  used  in  1886.  Here  series  parallel  grouping 
of  both  batteries  and  motor  circuits  were  used  on  the  Sprague  car, 
and  a  series  parallel  and  resistance  variation  of  motors  on  the  car 
operated  by  Reckenzaun  and  Condi ct. 

Meanwhile,  in  the  United  States,  Charles  J.  Van  Depoele,  a  Bel- 
gian by  birth  and  a  sculptor  by  original  trade,  and  an  indefatigable 
worker,  had  become  interested  in  electric  manufacturing,  and  soon 
energetically  attacked  the  railway  problem.  His  first  railway  was 
a  small  experimental  line  constructed  in  Chicago  in  the  winter  of 
1882-83,  the  current  being  supplied  from  an  overhead  wire.  In 
the  fall  of  1883,  a  car  was  also  run  at  the  Industrial  Exposition 
at  Chicago. 

A  year  later  a  train  pulled  by  a  locomotive  car,  and  taking  cur- 
rent from  an  underground  conduit,  was  successfully  operated  at 
the  Toronto  Exhibition  to  carry  passengers  from  the  street  car  sys- 
tem, and  again  in  the  year  following  Van  Depoele  operated  another 
train  at  the  same  place,  using  on  this  occasion  an  overhead  wire 
and  a  weighted  arm  pressing  a  contact  up  against  it. 

Experiments  were  also  carried  on  by  him  on  the  South  Bend 
Railway  in  the  fall  of  1885,  where  several  cars  were  equipped  with 
small  motors,  and  also  in  Minneapolis,  where  an  electric  car  took 
the  place  of  a  steam  locomotive.  Other  equipments  were  operated 
a i  the  New  Orleans  Exhibition,  and  at  Montgomery,  Ala.,  where  the 


8  8PRAGUE:    ELECTRIC  RAILWAYS. 

current  was  at  first  taken  from  a  single-overhead  wire  which 
carried  a  traveling  trolley  connected  to  the  car  by  a  flexible  con- 
ductor. 

Other  equipments  were  put  in  operation  at  Windsor,  Ont., 
Detroit,  Mich.,  Appleton,  Wis.,  and  Scranton,  Pa. 

In  these  several  equipments  the  motors  were  placed  on  the  front 
platforms  of  the  cars,  and  connected  to  the  wheels  by  belts  or  chains. 
The  cars  were  headed  in  one  direction,  and  operated  from  one  end 
only. 

In  1888,  the  Van  Depoele  Company  was  absorbed  by  the  Thom- 
son-Houston, which  had  recently  entered  the  railway  field,  and 
Van  Depoele  continued  in  its  active  development  until  his  death 
in  1892. 

Among  the  early  American  workers  of  this  period,  none  was  for 
a  time  more  prominent  than  Leo  Daft,  who  after  considerable 
development  in  motors  for  stationary  work  took  up  their  applica- 
tion to  electric  railways,  making  the  first  experiments  toward  the 
close  of  1883  at  his  company's  works  at  Greenville,  N.  J.,  these 
being  sufficiently  successful  to  be  repeated  in  November  of  that 
year  on  the  Saratoga  and  Mt.  McGregor  road.  The  locomotive 
used  there  was  called  "  The  Ampere,"  and  pulled  a  full  sized  car. 
The  motor  was  mounted  on  a  platform,  and  connected  by  belts  to 
an  intermediate  shaft  carried  between  the  wheels,  from  which 
another  set  of  belts  lead  to  pulleys  on  the  driving  axles.  A  center 
rail  and  the  running  rails  formed  the  working  conductors.  Varia- 
tion of  speed  was  accomplished  by  variation  of  field  resistance, 
this  being  accentuated  by  the  use  of  iron  instead  of  copper  in  some 
of  the  coils. 

In  the  following  year  Daft  equipped  a  small  car  on  one  of  the 
piers  at  a  New  York  seaside  resort,  and  a  little  later  another  one 
at  the  Mechanic's  Fair  in  Boston,  the  motor  for  this  last  being 
subsequently  put  on  duty  at  the  New  Orleans  Exposition.  In  1885 
work  was  begun  by  the  Daft  Company  on  the  Hampton  Branch  of 
the  Baltimore  Union  Passenger  Eailway  Company,  where  in  August 
of  that  year  operations  were  begun,  at  first  with  two  and  a  year 
later  with  two  more  small  electric  locomotives  which  did  not  carry 
passengers  themselves,  but  pulled  regular  street  cars.  A  center  and 
the  running  rail  were  used  for  the  normal  distribution,  but  at 
crossings  an  overhead  conductor  was  installed,  and  connection  made 
to  it  by  an  arm  carried  on  the  car  and  pressed  up  against  it.  The 


SPRAGUE:     ELECTRIC  RAILWAYS.  * 

driving  was  by  a  pinion  operating  on  an  internal  gear  on  one  of 
the  axles. 

Daft's  most  ambitious  work  followed  when  a  section  of  the  Ninth 
Avenue  Elevated  Eoad  was  equipped  for  a  distance  of  2  miles,  on 
which  a  series  of  experiments  were  carried  on  during  the  latter 
part  of  1885,  with  a  locomotive  called  "  The  Benjamin  Franklin."' 
The  motor  was  mounted  on  a  platform  pivoted  at  one  end,  and 
motion  was  communicated  from  the  armature  to  the  driving  wheel 
through  grooved  friction  gears  held  in  close  contact  partly  by  the 
weight  of  the  machine  and  partly  by  an  adjustable  screw  device. 
This  locomotive,  pulling  a  train  of  cars,  made  several  trips,  but 
the  experiments  were  soon  suspended.  This  work  was  followed 
by  street  railway  equipments  at  Los  Angeles  and  elsewhere,  using 
double  overhead  wires  carrying  a  trolley  carriage. 

Meanwhile  Bentley  and  Knight,  after  some  experiments  in  the 
yards  of  the  Brush  Electric  Company  at  Cleveland  in  the  fall  of 
1883,  installed  a  conduit  system  in  August,  1884,  on  the  tracks- 
of  the  East  Cleveland  Horse  Eailway  Company.  The  equipped  sec- 
tion of  the  road  was  2  miles  long,  the  conduits  were  of  wood  laid 
between  the  tracks,  and  two  cars  were  employed  which  were  each 
equipped  with  a  motor  carried  under  the  car  body  and  transmitting 
power  to  the  axle  by  wire  cables. 

These  equipments  were  operated  with  varying  degrees  of  success 
during  the  winter  of  1884-85,  but  were  abandoned  later.  This 
work  was  followed  by  a  double  overhead  trolley  road  at  Woon- 
socket,  the  motors  being  supplied  by  the  Thomson-Houston  Com- 
pany, and  later  by  a  combined  double  trolley  and  conduit  road  at 
Allegheny,  Pa. 

In  1884,  Dr.  Wellington  Adams  of  St.  Louis  proposed  a  de- 
parture in  motor  mounting  which  recognized  the  necessity  of  re- 
moving the  motor  from  the  car  body  and  directly  gearing  it  to  the 
axle.  In  his  plan  the  field  magnets  were  carried  by  the  pedestals, 
and  inclosed  the  axle  on  which  the  armature  was  to  revolve,  its 
motion  to  be  transmitted  by  gearing.  The  method  was  impractica- 
ble, and  found  no  application. 

In  1884-85,  J.  C.  Henry  installed  and  operated  in  Kansas  City 
a  railway  supplied  by  two  overhead  conductors  on  each  of  which 
traveled  a  small  trolley  connected  to  the  car  by  a  flexible  cable. 
The  motor  was  mounted  on  a  frame  supported  on  the  car  axle,  and 
the  power  was  transmitted  through  a  clutch  and  a  nest  of  gears 
giving  five  speeds.  In  the  following  year  a  portion  of  another 


10  8PRAOUE:     ELECTRIC  RAILWAYS. 

road  was  equipped.  A  number  of  experiments  seem  to  have  been 
conducted  there,  and  on  some  the  rails  were  used  as  a  return.  The 
collectors  were  of  different  types,  and  it  is  said  that  among  others 
there  was  one  carried  on  the  car.  The  final  selection  was  a  trolley 
having  four  wheels  disposed  in  pairs  in  a  horizontal  plane,  carried 
by  and  gripping  the  sides  of  the  wires;  this  feature,  but  using  one 
wire  and  rail  return,  characterized  a  road  installed  by  Henry  in 
San  Diego,  Cal.?  opened  in  November,  1887. 

In  the  early  part  of  1885,  Sidney  H.  Short  began  a  series  of 
experiments  on  a  short  piece  of  track  in  Denver  which  was  fol- 
lowed by  the  construction,  in  conjunction  with  J.  W.  Nesmith,  of 
a  section  of  road  for  operation  on  the  series  system.  These  experi- 
ments were  continued  through  1885  and  1886,  and  were  repeated 
at  Columbus,  but  were  doomed  to  ultimate  failure  because  of  the 
principle  involved.  Subsequently  Short  adopted  the  multiple 
system  of  distribution,  and  for  a  time  essayed  the  use  of  gearless 
motors  for  tramway  work,  but  reverted  later  to  the  geared  type. 

Meanwhile  work  had  begun  in  Great  Britain,  where  the  first 
regular  road  to  be  put  in  operation  was  that  known  as  the  Portrush 
Electric  Eailway,  in  Ireland,  installed  in  1883  by  Siemens  Brothers 
of  London.  Power  was  generated  by  turbines,  and  the  current  was 
transmitted  by  a  third  rail  supported  on  wooden  posts  alongside 
of  the  track,  the  running  rails  constituting  the  return.  The  pres- 
sure used  was  about  250  volts. 

This  was  followed  in  the  same  year  by  a  successful  short  road 
at  Brighton,  installed  by  Magnus  Volk,  the  current  being  trans- 
mitted through  the  running  rails.  Then  came  the  railway  in- 
stalled at  Bessbrook,  Newry,  in  1885,  under  the  direction  of  the 
Messrs.  Hopkinson,  and  at  Eyde,  in  1886,  in  which  latter  year  was 
also  installed  the  Blackpool  road  by  Holroyd  Smith.  In  this  latter 
case  the  conduit  system  was  used  with  complete  metallic  circuit. 
The  motor  was  carried  underneath  the  car  between  the  axles,  and 
connected  by  chain  gearing.  Fixed  brushes  with  end  contact  were 
used  for  both  directions  of  running. 

Eeverting  to  work  in  the  United  States,  Sprague  again  took  up 
the  electric  railway  problem,  and  in  1885,  before  the  Society  of 
Arts,  Boston,  advocated  the  equipment  of  the  New  York  Elevated 
Eailway  with  motors  carried  on  the  trucks  of  the  regular  cars, 
and  work  was  actually  begun  on  the  construction  of  experimental 
motors.  Shortly  afterward  a  regular  truck  was  equipped,  and  a  long 
series  of  tests  made  on  a  private  track  in  New  York  city.  In  May, 


8PRAGUE:     ELECTRIC  RAILWAYS.  11 

1886,  an  elevated  car  was  equipped  with  these  motors,  and  a  series 
of  tests  begun  on  the  Thirty-fourth  Street  branch  of  the  road. 

These  motors  may  be  considered  the  parent  models  of  the  modern 
railway  motor.  They  were  centered  through  the  brackets  on  the 
driving  axles,  connected  to  them  by  single  reduction  gears,  and 
the  free  end  of  the  motor  was  carried  by  springs  from  the  transom, 
the  truck  elliptics  being  interposed  between  this  support  and  the 
car  body.  The  truck  had  two  motors,  they  were  run  open,  had  one 
set  of  brushes,  and  were  used  not  only  for  propelling  the  car  but 
for  braking  it.  The  motors  were  at  first  shunt  wound,  but  later 
had  a  correcting  coil  in  series  with  the  armature  at  right  angles  to 
the  normal  field  to  prevent  shifting  of  the  neutral  point.  The  car 
was  operated  from  each  end  by  similar  switches,  current  at  600 
volts  were  used,  and  increase  of  speed  was  effected  by  cutting  out 
resistance  in  the  armature  circuit  and  then  by  reducing  the  field 
strength.  This  enabled  energy  to  be  returned  to  the  line  when 
decreasing  from  high  speed.  It  being  impossible  to  interest  the 
railway  management,  the  experiments  were  finally  suspended. 
Soon  afterward  a  locomotive  designed  by  Field  had  a  short  trial 
on  the  same  section  of  the  Elevated. 

Sprague  then  turned  his  attention  to  building  a  locomotive  car  of 
300-hp  capacity,  each  truck  to  be  equipped  with  two  motors,  each 
having  a  pair  of  armatures  geared  to  the  axle,  but  this  evidently 
being  ahead  of  the  times,  and  the  possibilities  of  street  tramway 
traction  becoming  evident,  these  equipments  were  abandoned,  and 
he  began  the  development  of  the  type  of  motor  finally  used  in 
Richmond,  one  crude  form  of  which  was  first  used  in  storage 
battery  experiments  in  Philadelphia,  and  others  in  New  York  and 
Boston,  in  1886.  One  of  the  Elevated  motors  was  put  into  ser- 
vice at  the  East  Boston  Sugar  Refinery,  and  continued  so  for  some- 
time. 

Reviewing  the  conditions  at  the  beginning  of  1887,  statistics 
compiled  by  Mr.  T.  Commerford  Martin  show  that,  including  every 
kind  of  equipment,  even  those  a  fraction  of  a  mile  long  and 
operated  in  mines,  there  were  but  nine  installations  in  Europe, 
aggregating  about  20  miles  of  track,  with  a  total  equipment  of  52 
motors  and  motor  cars,  none  operated  with  the  present  overhead 
line  or  conduit,  and  seven  cars  operated  by  storage  batteries,  while 
in  the  United  States  there  were  only  ten  installations,  with  an  ag- 
gregate of  less  than  40  miles  of  track  and  50  motors  and  motor 
cars,  operated  mostly  from  overhead  lines  with  traveling  trolleys 


12  SPRAGUE:     ELECTRIC  RAILWAYS. 

flexibly  connected  to  the  cars.  These  were  partly  Daft,  but  prin- 
cipally Van  Depoele  roads.  Almost  every  inventor  who  had  taken 
part  in  active  work  was  still  alive.  The  roads,  however,  were  limited 
in  character,  varied  in  equipment,  and  presented  nothing  sufficient 
to  overcome  the  prejudices  of  those  interested  in  transportation,  and 
command  the  confidence  of  capital.  The  whole  electric  railway 
art  may  fairly  be  termed,  and  was  in  fact  for  sometime  afterward,, 
in  an  experimental  condition,  and  some  radical  step  was  necessary 
to  overcome  the  inertia  which  existed,  and  inaugurate  that  develop- 
ment which  has  been  so  remarkable. 

This  came  in  the  spring  of  1887,  when  the  Sprague  Electric 
Railway  &  Motor  Company  took  contracts  for  roads  at  St.  Joseph,. 
Mo.,  and  Richmond,  Va.,  the  latter  covering  a  road  not  then  built,. 
and  including  a  complete  generating  station,  erection  of  overhead 
lines,  and  the  equipment  of  40  cars  each  with  two  7  1/2-hp  motors,, 
on  plans  largely  new  and  untried.  The  price,  terms,  and  guaran- 
tees were  such  as  to  impose  upon  the  company  extreme  hazards,, 
both  electrical  and  financial.  The  history  of  the  Richmond  road  has 
been  too  often  written  to  dwell  upon  it  at  any  length  here.  Suffice 
it  to  say  that  after  experimental  runs  in  the  latter  part  of  1887 
it  was  put  into  commercial  operation  in  the  beginning  of  February, 
1888,  and  for  a  year  there  followed  an  experimental  period  of 
development  which  taxed  the  technical  and  financial  resources  of 
the  company  to  the  limit.  But  it  won  out,  and  Richmond,  by  com- 
mon consent  of  history,  now  stands  as  that  pioneer  road  which 
more  than  any  other  was  effective  in  the  creation  of  the  electric- 
railway  as  it  stands  today. 

The  general  features  characterizing  it  may  be  briefly  summarized 
as  follows:  A  system  of  distribution  by  an  overhead  line  carried 
over  the  center  of  the  track,  reinforced  by  a  continuous  main  con- 
ductor, in  turn  supplied  at  central  distributing  points  by  feeders 
from  a  constant  potential  plant  operated  at  about  450  volts,  with 
reinforced  track  return.  The  current  was  taken  from  the  over- 
head line  at  first  by  fixed  upper  pressure  contracts,  and  subsequently 
by  a  wheel  carried  on  a  pole  supported  over  the  center  of  the  car 
and  having  free  up  and  down  reversible  movement,  exposed  motors, 
one  to  each,  were  centered  on  the  axles,  and  geared  to  them 
at  first  by  single,  and  then  by  double  reduction  gears,  the  outer  ends 
being  spring  supported  from  the  car  body  so  that  the  motors  were 
individually  free  to  follow  every  variation  of  axle  movement,  and 
yet  maintain  at  all  times  a  yielding  touch  upon  the  gears  an  abso- 


SPRAGUE:     ELECTRIC  RAILWAYS.  13 

lute  parallelism.  All  the  weight  of  the  car  was  available  for  trac- 
tion, and  the  cars  could  be  operated  in  either  direction  from  either 
end  of  the  platform.  The  controlling  system  was  at  first  by  graded 
resistances  affected  by  variation  of  the  field  coils  from  series  to 
multiple  relations,  and  series-parallel  control  of  armatures  by  a 
separate  switch.  Motors  were  run  in  both  directions  with  fixed 
brushes,  at  first  laminated  ones  placed  at  an  angle,  and  later 
solid  metallic  ones  with  radial  bearing. 

The  well-nigh  heart-breaking  experiences  and  the  alternation  of 
good  and  bad  performances  are  largely  matters  of  personal  history, 
but  the  results  accomplished  soon  commanded  the  attention  of 
those  interested  in  the  street  transportation,  most  prominent  among 
whom  at  that  time  was  Henry  M.  Whitney,  President  of  the  West 
End  Railway  of  Boston,  who  was  considering  the  adoption  of  the 
cable.  He  consented  to  come  to  Richmond,  and  accompanied  by  his 
associates  stopped  also  at  Allegheny  City  to  see  the  underground 
conduit  of  the  Bentley-Knight  Company.  The  demonstrations 
made  for  his  benefit  were  conclusive,  the  cable  was  abandoned,  and 
orders  given  for  trial  installations  on  both  the  overhead  and  under- 
ground systems  to  run  from  the  Providence  depot  in  Boston  to 
the  suburb  of  Allston.  A  winter's  run  resulted  in  the  abandon- 
ment of  the  conduit  and  the  adoption  of  the  overhead  trolley  sys- 
tem, the  principal  orders  for  equipment  going  to  the  Thomson- 
Houston  Company  which,  having  absorbed  the  Van  Depoele  Com- 
pany, was  now  pushing  work'  energetically.  Mr.  Whitney's  decision 
had  a  vital  bearing  upon  the  commercial  development  of  electric 
railways,  and  from  that  time  there  followed  a  period  of  extraor- 
dinary activity,  in  which  for  a  time  two  companies,  the  Sprague 
Electric  Railway  &  Motor  Company  and  the  Thomson-Houston 
Electric  Company,  were  the  principle  competitors.  There  was  a 
continuous  improvement  and  increase  in  the  size  of  apparatus. 
Form  wound  armatures,  proposed  by  Eickemeyer,  replaced  irregular 
windings,  and  metallic  brushes  gave  way  to  carbon,  this  single 
change,  initiated  by  Van  Depoele  in  1888-9,  going  a  long  way  to- 
ward making  the  art  a  success.  Cast  and  wrought  iron  yielded  to 
steel,  two-pole  motors  to  four-pole,  double  reduction  gears  to  single, 
and  open  motors  to  closed,  protected  only  by  their  own  casings.  In 
1892  combined  series  parallel  and  resistance  control  was  adopted, 
when  the  Thomson  magnet  blow-out  was  successfully  applied  to 
controllers  by  Mr.  Potter,  and  this  was  a  most  effective  agent  in 
reducing  the  troubles  of  operation. 


14  8PRAGUE:     ELECTRIC  RAILWAYS. 

The  progress  of  the  electric  railway,  however,  was  not  unimpeded, 
for  no  sooner  had  the  Kichmond  road  started  than  there  was  em- 
phasized a  series  of  disturbances  on  the  telephone  lines  which 
threatened  the  use  of  the  rails  for  return,  and  brought  on  a  con- 
flict with  the  Bell  Telephone  Company,  far  reaching  in  its  char- 
acter and  involving  new  legal  questions.  At  that  time  it  was 
almost  universal  practice  for  the  telephone  to  be  installed  with 
single  circuits  and  earth  return.  Already  the  service  had  become 
most  unsatisfactory  because  of  the  multiplicity  of  electric  install- 
ations of  various  kinds,  with  consequent  leakages,  troubles  from 
induction  and  variations  in  earth  potential.  To  the  hissing  and 
frying  incident  to  the  system  as  installed  was  now  added  the  hum 
of  the  motor  and  exaggerated  differences  of  potential  at  the  ground 
connections. 

The  first  attempt  to  meet  this  was  made  in  Eichmond  by  the 
superintendent  of  the  exchange,  who  disconnected  from  the  ground 
and  joined  all  return  wires  to  a  common  circuit.  This  obviated 
most  leakage  troubles,  but  did  not  get  rid  of  the  troubles  of  in- 
duction. Numerous  law  suits  followed  in  nearly  half  the  States 
of  the  Union,  the  telephone  companies  attempting  to  force  the 
railways  to  use  double  overhead  circuits,  and  the  railway  companies 
demanding  their  share  of  the  heritage  of  the  earth.  The  trolley 
contentions  were  in  the  main  successful,  and  individual  metallic 
circuits,  vital  to  successful  operation,  and  without  which  long  dis- 
tance telephone  is  impracticable,  were  adopted,  for  which  condition 
of  affairs  the  electric  railway  may  be  thanked. 

The  work  accomplished  at  Eichmond,  the  widespread  advertising 
of  the  equipment  and  the  rapid  spread  of  electric  railways  in  the 
United  States  commanded  the  attention  of  the  Old  World,  and 
work  was  begun  in  Italy,  Germany  and  elsewhere  along  the  same 
lines,  but  it  was  not  until  a  number  of  years  later  that  there  was 
any  general  adoption  of  the  electric  railway  in  the  more  conserv- 
ative countries. 

Meanwhile  the  Sprague  Electric  Eailway  &  Motor  Company 
was  absorbed  in  1890  by  the  Edison  General  Electric,  which  later 
combined  with  the  Thomson-Houston  Company  and  others  in  the 
General  Electric. 

For  the  next  six  years  the  record  of  the  electric  railway  is  that 
of  industrial  development,  practically  as  indicated  in  the  improve- 
ment of  apparatus,  the  replacement  of  horse  and  cable  power  on 
existing  lines,  and  the  creation  of  new  ones.  Electric  operation 


SPRAGUE:     ELECTRIC  RAILWAYS.  15 

on  tramways  having  become  established,  there  naturally  followed 
more  ambitious  attempts  in  limited  applications  of  electricity  to 
heavier  work. 

In  November,  1890,  a  line  on  South  London  road,  which  was 
originally  designed  for  cable,  was  opened,  the  trains  being  pulled 
by  electric  locomotives  equipped  with  a  pair  of  gearless  motors 
having  armatures  mounted  on  the  axles  of  the  drivers. 

In  June,  1891,  Sprague  offered  to  install  on  the  New  York 
Elevated  road  a  train  to  be  operated  by  a  locomotive  car,  and  also 
one  with  motors  distributed  under  the  cars,  and  to  make  an  express 
speed  of  40  miles  an  hour.  Two  years  later  the  Liverpool  overhead 
railway  was  put  in  operation.  Here  the  trains  were  composed  of 
two-car  units,  each  car  having  one  motor,  the  two  being  operated 
by  hand  control. 

In  the  spring  of  the  same  year,  1893,  the  Intramural  Kailway 
was  constructed  at  the  World's  Fair,  the  equipment  being  supplied 
by  the  General  Electric  Company.  Four  motor  cars  with  hand 
control  were  used  to  pull  three  trail  cars,  and  a  third-rail  supply 
with  running-rail  return  was  adopted.  Two  years  later  the  Met- 
ropolitan West  Side  Elevated  road  in  the  same  city  was  equipped 
on  the  same  general  plan  except  using  two  motors  instead  of  four. 

In  May,  1896,  the  Nantasket  Beach  road,  a  branch  of  the  New 
York  &  New  Haven  Kailway,  was  put  in  operation,  and  in  Sep- 
tember the  Lake  Street  Elevated  of  Chicago  began  electrical  oper- 
ations. In  November  of  the  same  year,  electric  service  was  in- 
stituted on  the  Brooklyn  Bridge,  the  motor  cars  being  used  to 
handle  the  trains  at  first  at  the  terminals  but  later  across  the 
bridge. 

There  were  few  attempts,  however,  to  replace  steam  on  regular 
roads,  and  only  occasionally  were  electric  locomotives  adopted  for 
special  reasons.  Among  the  earlier  ones  built  were  one  of  1000 
horsepower,  1892-94,  designed  by  Sprague,  Duncan  and  Hutchin- 
son  for  Mr.  Henry  Villard  for  experimental  operation  on  lines  out 
of  Chicago,  which  was  never  undertaken,  and  the  still  larger  loco- 
motives built  by  the  General  Electric  Company,  which  began 
operation  of  the  trains  in  the  Baltimore  &  Ohio  tunnel  in  1895. 

For  a  long  time  the  conduit  system,  after  its  abandonment  at 
Allegheny  and  Boston,  remained  quiescent,  and  all  work  was  practi- 
cally with  the  overhead  trolley.  In  1893  a  short  line  was  tried  in 
Washington  on  the  Love  system,  but  it  was  not  until  the  following 
year  that  work  was  begun  in  New  York  on  the  Lenox  Avenue 


16  8PRAOUE:     ELECTRIC  RAILWAYS. 

line,  and  carried  to  that  successful  conclusion  which  warranted  its 
widespread  adoption  in  that  city,  under  the  auspices  of  Wm. 
Whitney  and  Henry  Vreeland,  and  in  Washington  under  Con- 
nett,  although  a  line  had  been  in  operation  at  Budapest  for 
some  time.  All  this  of  course  was  largely  because  of  the  necessary 
•cost  of  the  heavy  construction,  and  because  street  railway  man- 
agers would  not  and  could  not  undertake  any  such  investment 
except  under  most  favorable  traffic  conditions,  and  then  with  the 
additional  restriction  of  a  prohibition  of  the  use  of  overhead 
wires. 

About  this  period  there  began  that  rapid  introduction  of  inter- 
urban  railways,  soon  aided  by  the  developments  in  transformers  by 
Stanley,  in  polyphase  transmission  by  Tesla  and  Ferraris,  and  in 
rotary  transformers  by  Bradley  and  others,  which  has  had  sucE  an 
influence  upon  steam  railway  operation  and  been  so  instrumental 
in  knitting  together  urban  and  rural  communities. 

The  first  practical  proposal  for  a  railway  using  high-tension 
alternating-current  transmission,  seems  to  have  been  made  in  1896 
by  Bion  J.  Arnold  in  plans  for  a  road  to  run  from  Chicago  to  the 
Lake  region,  and  although  this  road  was  never  built  the  general 
plans  were  utilized  for  a  line  actually  put  into  operation  about  two 
years  later,  which  was  the  forerunner  of  the  standard  practice  of 
today  by  means  of  which  the  limitations  of  distance  have  been  so 
effectively  reduced. 

In  1896  Sprague  again  sought  the  opportunity  to  make  a 
•demonstration  on  the  Elevated  Eailway  in  the  form  of  a  proposition 
to  the  management  to  equip  a  section  of  the  line,  and  operate  a 
train  of  cars  on  a  new  principle,  the  "  Multiple  Unit." 

Although  the  advantages  of  the  system,  such  as  higher  schedules, 
reduced  weights,  variable  train  lengths,  more  frequent  trains,  dis- 
tributive motive  equipment  and  increased  economy  were  presented, 
.and  supplemented  by  an  offer  to  equip  the  whole  system,  no  re- 
sponse whatever  was  made.  A  similar  proposal  repeated  seven 
months  later  met  with  like  fate,  but  in  the  spring  of  1897  he  made 
a  contract  with  the  South  Side  Elevated  Kailfoad,  in  Chicago,  to 
equip  the  line  on  this  plan  in  lieu  of  the  locomotive  car  plan  then 
under  consideration. 

This  system  has  now  become  so  widely  known  that  any  detailed 
description  of  it  is  unnecessary.  Generally  speaking,  however, 
it  is  essentially  the  control  of  controllers,  by  means  of  which  cars 
equipped  with  motors  and  controllers  for  them  are  operated  from 


SPRAGUE:     ELECTRIC  RAILWAYS.  17 

master  switches  through  a  secondary  line,  with  provision  for  so 
coupling  up  cars  that  from  any  master  switch  all  cars  can  be  oper- 
ated irrespective  of  number,  order  or  end  relation,  or  whether  all  or 
only  part  of  the  cars, are  equipped  with  motors. 

The  first  equipment  was  for  120  cars,  and  the  first  public 
demonstration  was  made  in  July,  1887,  at  Schenectady,  on  a  full 
train  of  cars  which  had  been  sent  from  Chicago  for  that  purpose. 
A  regular  train  was  put  into  operation  before  the  close  of  the  year, 
and  within  a  few  months  steam  operation  was  entirely  replaced, 

As  originally  equipped,  the  main  controller  consisted  of  a  mag- 
net-operated reverser  and  pilot-motor  driven  cylinder,  operated 
semi-automatically  and  with  throttle  restraint  through  a  secondary 
line  and  relays  from  master  switches  on  the  platforms.  A  number 
of  variations  have  since  been  developed,  such  as  operating  the 
reverser  and  cylinder  by  air  pistons  electrically  controlled,  or 
breaking  the  main  controller  up  into  several  magnetically  operated 
parts,  and  all  forms  of  equipment  are  now  in  operation.  The  es- 
sential principle  of  the  system,  however,  has  not  been  changed, 
and  it  has  become  standard  wherever  required  to  operate  electric 
trains  at  high  schedules.  Equipments  have  grown  from  100  horse- 
power per  car  to  2200  horse-power  per  locomotive,  for  in  the  largest 
work  under  way,  that  of  the  New  York  Central,  the  locomotives  are 
to  be  controlled  on  this  plan. 

The  necessities  of  tunnel  traffic  on  the  one  hand  and  a  grave 
accident  on  the  other  have  curiously  enough  centered  in  New  York 
the  largest  two  electric  transportation  problems,  namely,  that  of 
the  operation  of  the  Pennsylvania  tunnel  and  terminals,  and  more 
extensive  still,  that  of  the  New  York  &  Hudson  Eiver  Kailroad  for 
35  miles  out  from  its  terminals.  The  general  requirements  are 
so  exacting,  and  the  installation  of  the  latter  under  such  difficult 
continuous  working  conditions  that  they  will  prove  of  historic  in- 
terest, and  be  influential  in  determining  the  disposition  of  many 
terminal  problems. 

Up  to  comparatively  recent  times  most  of  the  electric  railways, 
including  those  just  mentioned,  have  been  planned  for  operation 
with  continuous  current  motors  at  moderate  potentials,  but  this 
has  often  required  the  conversion  of  alternating  current  trans- 
mitted at  high  potential  into  continuous  current  at  a  lower  one 
through  the  medium  of  transformers  and  rotary  converters.  While 
this  bids  fair  to  be  the  practice  for  some  time,  there  are  of  course 
certain  objections  which  are  apparent,  and  the  best  energies  of  many 

KI.F.C.    RYS. 2. 


18  SPRAGUE:     ELECTRIC  RAILWAYS. 

of  the  ablest  electrical  engineers  have  for  some  time  been  bent  upon 
solving  the  problem  of  operating  directly  with  alternating  cur- 
rents. Among  the  most  active  and  successful  of  these  have  been  the 
Ganz  Company,  whose  Valtellina  line,  equipped  on  the  polyphase 
plan  for  Italian  Government,  is  of  special  interest.  Among  note- 
worthy experimental  installations  is  that  conducted  under  the 
auspices  of  the  German  Government  on  the  Zossen  military  line, 
where  the  highest  record  for  speed  of  a  car  carrying  passengers, 
about  126  miles  per  hour,  has  been  made  during  the  past  year,  the 
current  being  collected  frpm  the  three  overhead  wires  by  sliding 
contacts. 

The  multiplicity  of  conductors,  however,  distinctly  militates 
against  this  as  any  general  solution  of  the  larger  railway  problems, 
quite  independently  of  other  limitations  affecting  trunk-line  trans- 
portation, and  hence  single-phase  operation,  using  one  overhead 
conductor  with  track  return,  is  being  energetically  prosecuted. 
Among  the  workers  who  have  sought  solution  and  been  active  in 
invention  along  this  line,  as  well  as  one  of  the  earliest  and  most 
persistent  advocates  of  single-phase  railway  operation,  is  Mr. 
Arnold,  who  has  developed  an  electro-pneumatic  plan  in  which 
is  combined  on  a  locomotive  a  constant  speed  single-phase  alternat- 
ing-current motor  with  reversible  air  pumps  and  a  storage  tank,  by 
which  starting  and  running  can  be  controlled  by  compressed  air 
with  a  more  even  demand  upon  the  capacity  of  the  station.  Arnold's 
experiments,  a  long  time  delayed  from  various  causes,  are  now 
being  subjected  to  the  actual  tests  which  will  demonstrate  the 
practicability  of  this  scheme.  Meanwhile,  becoming  alive  to  the 
limitations  of  past  practices  and  the  increasing  demands  of  the  art, 
the  engineers  of  the  various  manufacturing  companies  in  the 
United  States  and  Europe,  among  whom  must  be  especially  men- 
tioned Finzi,  Lamme,  Latour,  Winter,  Eichberg  and  Steinmetz,  are 
developing  the  single-phase  alternating-current  motor  along  two 
general  lines.  One  is  by  using  a  series  motor  of  special  construc- 
tion, plain  or  compensated  current  being  supplied  from  the  second- 
ary of  a  transformer  carried  on  the  car  and  operated  at  moderate 
frequency.  Another  form  is  that  originally  proposed  by  Thomson, 
and  known  as  the  "  repulsion  "  type,  in  which  the  field  is  supplied 
directly  at  high  potential,  and  the  armature  is  short-circuited  upon 
itself  and  operates  at  low  potential.  An  alternative  of  this  form  is 
that  developed  by  European  engineers,  in  which  a  variable  potential 
is  delivered  to  the  armature  from  a  transformer,  the  field  being 


SPRAGUE:     ELECTRIC  RAILWAYS.  ID 

supplied  direct  from  the  line.  One  desideratum  is  of  course  to  be 
able  to  operate  both  from  alternating  and  continuous  currents,  and 
this  has  been  done,  but  the  best  results  may  possibly  be  gotten  by 
ignoring  this  limitation. 

It  is  unnecessary  to  go  into  the  many  variations  or  details  of 
these  various  schemes.  Suffice  it  to  say  that  all  are  being  sub- 
mitted to  the  crucial  test  of  commercial  operation,  and  the  over- 
coming of  difficulties  of  the  early  days  of  electric  railroading  war- 
rant expectation  that  a  great  measure  of  success  will  likewise  be 
attained  on  these  new  lines,  and  that  another  bar  to  the  wider 
spread  of  electric  railway  operation  may  be  speedily  removed. 

This  paper  will  not  be  burdened  with  detail  statistics,  but  to 
illustrate  in  a  general  way  the  growth  of  the  electric  railway  it 
should  be  noted  that  three  years  after  the  inauguration  of  the  Kich- 
mond  road  there  were  in  operation  or  under  contract  in  the  United 
States,  England,  Germany,  Italy  and  Japan,  not  less  than  325 
roads,  representing  an  equipment  of  about  4000  cars  and  7000 
motors,  with  2600  miles  of  track,  on  which  there  was  made  a 
daily  mileage  of  not  less  than  400,000  miles,  and  three-quarters  of  a 
billion  of  passengers  were  carried  annually. 

By  the  end  of  1903,  in  the  United  States  alone,  there  was  a 
total  of  over  29,000  miles  equipped,  60,000  motors  and  12,000  trail 
and  service  cars  in  service,  and  the  passengers  carried  ran  into 
billions. 

What  the  electric  railway  has  done  may  only  briefly  be  referred 
to  here,  but  the  writer  may  be  permitted  to  repeat  the  substance  of 
remarks  written  some  nine  years  ago,  for  it  has  become  a  most 
potent  factor  in  our  modern  life,  and  left  its  imprint  in  the  indelible 
stamp  of  commercial  supremacy.  It  has  given  us  better  paved 
streets,  greater  cleanliness,  more  perfect  tracks,  and  luxurious, 
well-lighted  and  well-ventilated  cars.  With  the  higher  speeds 
it  has  made  possible  the  extension  of  the  taxable  and  habitable 
areas  of  towns  and  cities  in  a  much  greater  ratio  than  is  repre- 
sented by  the  increase  of  speed. 

It  has  released  from  -drudgery  tens  of  thousands  of  animals,  and 
increased  the  morale  of  transportation  employees.  It  has  given 
employment  to  an  army  of  men,  and  hundreds  of  millions  of  capi- 
tal. It  has  improved  and  extended  the  telephone  service  by  forc- 
ing the  abandonment  of  ground  circuits.  It  has  built  up  com- 
munities, shortened  the  time  between  home  and  business,  made 


20  8PRAGUE:     ELECTRIC  RAILWAYS. 

neighbors  of  rural  communities,  and  welded  together  cities  and 
their  suburbs. 

Will  it  replace  the  steam  locomotive? 

Perhaps  the  best  answer  is  that  "  its  future  is  not  in  the  whole- 
sale destruction  of  existing  great  systems.  It  is  in  the  development 
of  a  field  of  its  own,  with  recognized  limitations  but  of  vast  possibil- 
ities. It  will  fill  that  field  to  the  practical  exclusion  of  all  other 
methods  of  transmitting  energy;  it  will  operate  all  street  railway 
systems,  and  elevated  and  underground  roads ;  it  will  prove  a  valu- 
able auxiliary  to  trunk  systems;  but  it  has  not  yet  sounded  the 
death-knell  of  the  locomotive  any  more  than  the  dynamo  has  that 
of  the  stationary  steam  engine.  Each  has  its  own  legitimate  field." 


SOME  EAELY  WORK  IN  POLYPHASE  AND 
SINGLE-PHASE  ELECTRIC  TRACTION. 


BY  BION  J.  ARNOLD. 


In  1896  I  became  interested  in  a  proposed  road  projected  to 
run  west  and  north  from  Chicago  into  the  lake  regions  of  Wiscon- 
sin, and  to  be  known  as  the  Wisconsin  Inland  Lakes  &  Chicago 
Electric  Eailway. 

The  rotary  converter  was  then  just  beginning  to  be  commercially 
exploited,  and  had,  I  believe,  been  used  in  some  instances  for  power 
transmission,  but  so  far  as  I  know  it  had  not  been  used  for  railway 
work.  Desiring  to  construct  the  road,  some  75  miles  in  length, 
as  economically  as  practicable,  and  seeing  no.  reason  why  rotary 
converters  would -not  operate  on  railway  work,  I  decided  to  adopt 
a  three-phase  high-tension  transmission  system  with  sub-stations, 
using  rotary  converters  and  storage  batteries  —  a  radical  depart- 
ure from  the  then  standard  500-volt  direct-current  system. 

Complete  detailed  specifications  for  the  road  and  its  equipment 
were  prepared,  calling  for  three-phase  generators  capable  of  sup- 
plying current  at  1040  volts,  the  necessary  step-up  and  step-down 
transformers,  switchboard  apparatus,  rotary  converters,  etc.,  re- 
quired to  generate  alternating-current  energy  at  1040  volts,  trans- 
mit it  at  5000  volts,  and  convert  it  into  direct  current  at  700 
volts  to  supply  the  overhead  conductor,  from  which  standard 
direct-current  railway  motors  were  to  be  operated,  using  storage 
batteries  as  equalizers  in  sub-stations  distributed  along  the  line. 

Fig.  1,  which  shows  the  arrangement  proposed,  is  a  reproduction 
of  one  of  the  original  drawings  attached  to  the  specifications  sub- 
mitted to  the  railway  company  at  the  time  the  final  specifications 
were  delivered. 

It  happened,  unfortunately,  that  the  promoters  of  the  road 
were  unable  to  secure  the  necessary  franchises  for  its  construction, 
and  it  remains  unbuilt  today,  while  the  specifications  and  plans 
repose  among  the  archives  of  my  office  as  evidence  that  an  engineer, 

[21] 


22       ARNOLD:     POLYPHASE  AND  SINGLE-PHASE  TRACTION 


eager  to  see  his  ideas  executed,  is  apt  sometimes  to  do  much  work 
for  no  pay  and  stand  the  preliminary  expenses  himself.  The  ter- 
ritory has  since  been  partially  occupied  by  the  Aurora,  Elgin  & 
Chicago  Electric  Railway,  and  the  Chicago  &  Milwaukee  Electric 
Railroad. 

However,  while  this  experience  was  somewhat  disappointing 
financially,  the  time  and  study  put  upon  it  were  not  lost.  A  few 
months  later  the  promoters  of  another  road,  now  a  part  of  the 
Chicago  &  Milwaukee  Electric  Railroad,  came  and  stated  that  they 
must  build  15  miles  of  new  road  in  order  to  connect  two  small 
roads,  each  about  a  mile  long,  and  that  out  of  the  total  money 


Distance* 
JbtropoUtan  Road  to  Elgin 

-<•  Power  House  12  MU 

..  H     "  Wilmot  54  MU 

Elgin  Branch  20  MU 

Total  length  of  road  74  MU 


FIG.  1. —  MAP  SHOWING  LOCATION  OF  POWER-HOUSE;  SUBSTATION  AND  DIS- 
TRIBUTION SYSTEM  OF  THE  WISCONSIN  INLAND  LAKES  &  CHI- 
CAGO ELECTRIC  RAILWAY  AS  PLANNED  IN  1896. 

available  to  build  this  road  they  had  provided  but  $10,000  to  put 
into  copper.  After  carefully  calculating  the  cost  of  the  road 
and  finding  it  prohibitive,  if  built  under  the  then  standard  500- 
volt  direct-current  system  of  distribution,  the  plans  of  the  Inland 
Lakes  Road  were  resurrected.  To  have  built  the  new  road  under 
the  500-volt  direct-current  system  would  have  necessitated  in- 
vesting almost  as  much  money  for  copper  alone  as  the  parties  had 
at  their  disposal  for  building  the  complete  electrical  and*  mechani- 
cal equipment. 


ARNOLD:     POLYPHASE  AND  SINGLE-PHASE  TRAGTION.       9.3 

After  explaining  the  alternating-current  plan  and  showing  its 
adaptability  to  the  case,  and  the  impossibility  of  constructing  under 
the  standard  500-volt  system,  a  remark  was  made  by  one  of  the 
owners  to  the  effect  that :  "  If  the  engineer  was  willing  to  take  the 
professional  risk  the  owner  would  take  the  financial  risk."  Au- 
thority was  secured  to  build  in  accordance  with  the  rotary-con- 
verter plan  I  had  submitted,  on  condition  that  the  road  must  be 
in  operation  within  90  days,  in  order  to  save  the  franchises 
under  which  it  was  authorized. 

One  of  the  leading  manufacturing  companies  had  on  hand  at  this 
time  (March,  1898)  three  120-kw  rotary  converters,  which  had 
been  built  for  experimental  purposes  mainly,  and  by  contracting 
with  this  company  for  the  new  electrical  machinery  required  for 
the  road,  the  use  of  these  rotaries,  provided  with  temporary  trans- 
formers and  switchboard  apparatus,  was  secured. 

A  new  power-house  was  built,  a  transmission  line  eight  miles 
long,  consisting  of  three  No.  8  bare  copper  wires  carried  upon  or- 
dinary Western  Union  single-petticoat  glass  insulators,  was  con- 
structed, and  the  temporary  apparatus  installed. 

It  was  necessary  to  belt  two  of  -the  rotaries  in  tandem  from  the 
fly-wheel  of  the  engine,  and  use  them  as  generators,  one  supplying 
direct  current  to  the  section  of  the  line  nearest  the  power-house, 
while  the  other  supplied  three-phase  current  to  the  third  rotary 
placed  in  the  sub-station  eight  miles  away.  The  alternating  cur- 
rent was  stepped  up  at  the  power-house  and  transmitted  at  5000 
volts. 

The  road  was  opened  for  traffic  July  1,  1898,  and  ran  with  fair 
success  with  the  temporary  apparatus  until  the  following  spring. 

In  the  meantime  the  ownership  had  changed  hands,  and  the  new 
owners,  owing  to  their  unfamiliarity  with  electric  railways  and  the 
trouble  due  to  the.  temporary  character  of  the  plant  (the  new 
machinery  not  yet  having  been  received  from  the  manufacturers), 
desired  to  change  the  road  into  a  standard  direct-current  system, 
and  in  this  position  they  were  supported  by  several  engineers 
whom  they  consulted,  and  who  reported  adversely  to  the  new 
system.  It  was  also  intended  to  extend  the  road  southward  10 
miles  to  Evanston,  the  road  previous  to  this  time  having  extended 
only  from  Waukegan  to  Highland  Park,  a  distance  of  about 
15  miles.  In  order  to  prevent  the  abandonment  of  my  plans 
and  of  the  alternating  system  it  became  necessary  for  me  to 
assume  the  entire  risk,  and  a  contract  was  entered  into  whereby 


24       ARNOLD:     POLYPHASE  AND  SINGLE-PEASE  TRACTION. 

I  undertook  to  complete  and  extend  the  road  in  accordance  with 
the  original  designs  and  guarantee,  under  a  bonus  and  forfeiture 
contract,  a  certain  efficiency  between  the  steam-engine  cylinders 
and  the  car  motors  under  working  conditions,  and  the  successful 
operation  of  the  system  as  a  whole. 

The  contract  was  dated  March  21,  1899,  and  as  an  example  of 
how  rapidly  engineering  and  construction  work  can  be  done  when 
necessary,  I  will  state  that  the  conditions  of  the  contract  were 
successfully  met  on  time,  and  when  the  work  called  for  by  it  was 
completed  the  road  stood,  on  June  20, 1899,  equipped  with  a  central 
power  station,  and  two  sub-stations,  each  eight  miles  from  the 


DIAGRAM  OP  FEEDER  SYSTEM1. 

CHICAGO  AND  MILWAUKEE  ELECTRIC  R.JR. 

FlQ.   2. MAP    SHOWING   LOCATION   OF  POWER-HOUSE,    SUB-STATION    AND    DIS- 
TRIBUTION   SYSTEM    OF    THE    CHICAGO    &    MILWAUKEE    ELECTRIC 

RAILWAY  COMPANY,  AS  PLANNED  IN   1898  AND  COMPLETED  IN 
1899.    FIRST  ROTARY  CONVEETEB  SUB-STATION  ROAD. 


power-house,  all  equipped  with  new  machinery,  regulating  bat- 
teries, together  with  all  necessary  high-tension  transmission  lines 
and  direct-current  feeders  for  operating  16  40-ton  trains  be- 
tween Evanston  and  Waukegan,  a  distance  of  27  miles,  at  an 
average  speed  of  20  miles  per  hour,  with  stops  averaging  one  per 
mile. 

The  energy  was  generated  and  transmitted  at  5500  volts,  as  this 
was  the  highest  pressure  that  the  manufacturers,  whom  the  con- 
ditions made  it  desirable  to  contract  with  for  the  electrical  machin- 
ery on  account  of  their  experience  and  ability  to  make  prompt 
deliveries,  were  prepared  to  furnish  machinery  for  at  that  time. 


ARNOLD:     POLYPHASE  AND  SINGLE-PHASE  TRACTION.       23 


The  success  of  the  road  was  immediate,  and  its  traffic  has  grown 
so  rapidly  that  its  capacity  has  been  increased  to  three  times  its 
original  capacity,  during  the  past  year,  under  the  direction  of  my 
office. 

While  there  was  an  instance  of  a  one-car  road  at  Concord,  N.  H., 
taking  its  power  through  a  rotary  converter,  located  about  four 
miles  from  a  water-power  generating  station,  the  road  I  describe, 
I  believe,  was  the  first  road  to  be  put  in  operation  designed  to 


MILWAUKEE 


I  •  • 


RACINE 


KEN OS HA 


WAUKEGAN 

NORTH  CHICAGO 
LAKE  BLUFF 
LAKE  FOREST 
fORT  SHERIDAN 
i       tilGHWOOD 
tMGHLANO  PARK 
RAVINIA 
GLENCOE 
IAK6SIDE 
WINNETKA 
KCNIUWORTH 
WlLMETTt 
.•WRTh  EVANSTON 

EVANSTON" 


CHIC 


FlO.   3. —  MAP   SHOWING   GEOGRAPHICAL   LOCATION   OF   THE   CHICAGO   &  MIL- 
WAUKEE ELECTRIC  RAILWAY. 

run  from  a  central  alternating-current  power  station,  using  high- 
tension  transmission  lines,  rotary  converters  and  sub-stations. 

It  was  thus  probably  the  prototype  of  the  system  that  rapidly 
became  standard,  and  upon  which  almost  all  suburban  lines  have 
been  built  since. 

Fig.  2  is  a  map  of  the  road,  drawn  to  scale,  giving  the  relative 
locations  of  the  power-house  and  sub-stations,  and  is  a  reproduc- 
tion of  one  of  the  original  sketches  attached  to  the  contract  en- 
tered into  on  March  21,  1899.  The  portion  of  the  line,  north  of 
the  power-house  at  Highwood,  was  installed  during  the  previous 
year  and  equipped  with  the  temporary  machines. 


26       ARNOLD:     POLYPHASE  AND  SINGLE-PHASE  TRACTIOX. 

Fig.  3  shows  the  relative  location  of  the  road  to  the  surrounding 
territory. 

While  this  system  was  a  marked  step  in  advance  in  electric  rail- 
roading, effecting  as  it  did  a  great  reduction  in  first  cost  and  oper- 
ation, it  did  not  seem  to  me  to  be  the  final  solution  of  the  electric 
railway  problem  on  account  of  the  losses  due  to  the  many  conver- 
sions of  the  current  and  the  excessive  investment  in  sub-station 
machinery,  with  the  attendant  operating  expenses. 

In  1899,  while  still  engaged  upon  this  work,  I,  therefore,  com- 
menced to  develop  a  system  which  should  utilize  the  alternating 
current  directly  in  the  motor  and  employ  but  one  overhead  con- 
ductor, and  thus  eliminate  the  sub-station  completely,  together 
with  the  disadvantages  of  the  complicated  overhead  work  made 
necessary  by  the  use  of  three-phase  motors  as  then  applied  to  alter- 
nating-current railway  work  in  Europe.  Realizing  the  advantages 
that  storage  batteries  offered  for  equalizing  the  load  in  direct- 
current  work  I  planned  to  retain  a  similar  advantage  for  the 
alternating-current  system  by  utilizing  some  form  of  a  storage  sys- 
tem to  be  carried  upon  the  car.  As  the  single-phase  motor  was  not 
at  that  time  capable  of  self -starting  under  load,  some  supplemental 
means  must  be  provided  for  starting  it.  Air  was  the  medium 
chosen,  for  by  its  use  in  combination  with  a  high-tension  single- 
phase  motor  I  saw  a  possibility  of  requiring  not  only  a  single 
overhead  working  conductor,  but  of  maintaining  a  constant  load 
upon  the  power-house,  thus  enabling  the  investment  in  machinery 
and  transmission  lines  for  any  given  case  to  be  much  less  than  would 
be  possible  with  the  heavy  fluctuating  loads  common  to  all  electric- 
railway  systems.  The  essentials  decided  upon  were: 

(1)  A  motor  which  would  use  single-phase  alternating  current 
without  conversion. 

(2)  Single  overhead  working  conductor. 

(3)  Steady  load  upon  the  power-house. 

(4)  Independent  unit  for  switching  purposes. 

The  principles  underlying  the  system  which  I  developed  to 
accomplish  these  results  were: 

(a)  A  single-phase  motor  mounted  directly  upon  the  car  axles, 
designed  for  the  average  power  required  by  the  car,  running  at  a 
constant  speed  and  a  constant  load,  and,  therefore,  at  maximum 
efficiency. 


ARNOLD:     POLYPHASE  AND  SINGLE-PHASE  TRACTION.      27 

(ft)  Instead  of  stopping  and  starting  this  motor  and  dissipat- 
ing the  energy  through  resistance,  as  was  then  common  to  all  rail- 
way systems,  the  speed  of  the  car  was  controlled  by  accelerating 
or  retarding  the  parts  usually  known  as  the  rotor  and  the  stator, 
by  means  of  compressed  air  in  such  a  manner  as  not  only  to  regu- 
late the  speed  of  the  car  but  also  to  store  the  kinetic  energy  of  the 
car  when  stopping  and  utilize  it  in  starting. 

Draughtsmen  were  put  at  work  preparing  the  Patent  Office 
drawings  for  different  methods  of  applying  the  above  principles, 
and  late  in  1899  an  opportunity  for  trying  the  system  was  offered 
in  the  case  of  a  road  designed  to  extend  about  60  miles  northward 
from  Lansing,  Mich.,  and  to  be  known  as  the  Lansing,  St.  Johns  & 
St.  Louis  Electric  Railway.  In  January,  1900,  I  rode  over  the  pro- 
posed right  of  way  with  a  party  of  gentlemen  interested  in  the  road, 
and  as  a  result  of  the  negotiations  that  ensued  a  contract  for  its 


Wirt 


Maple  Rapid* 

I?IG.  4. —  MAP  SHOWING  LOCATION  OF  THE  LANSING,  ST.  JOHNS  &  ST.  Louis 
ELECTBIC  RAILWAY.    FIBST  SINGLE-PHASE  BOAD. 

construction  was  entered  into  on  April  23,  1900,  wherein  I  under- 
took to  build  the  road,  assuming  part  of  the  financial  risk. 

Fig.  4  is  a  reproduction  of  one  of  the  original  sketches  attached 
to  the  contract,  and  Fig.  5  is  a  map  showing  the  relative  location 
of  this  road  to  the  other  roads  in  the  State  of  Michigan. 

Locating  engineers  were  at  once  placed  in  the  field,  and  the 
construction  proceeded  systematically  until  20  miles  of  the  road 
(extending  from  Lansing  to  St.  Johns)  were  completed  to  such  an 
extent  that  it  was  opened  for  operation  with  steam  locomotives 
about  Nov.  15,  1901. 

For  financial  reasons  the  construction  work  was  delayed  but  in 
the  meantime  the  development  of  the  electrical  system  was  going 
on  in  different  offices  and  shops. 

The  overhead  work  of  the  20-mile  section  of  the  road  was  com- 
pleted and  ready  for  operation  about  Dec.  15,  1902,  and  the  power 
installed,  so  that  experiments  with  the  electropneumatic  system 
began  in  March,  1903.  During  these  and  all  subsequent  experi- 


28       ARNOLD:     POLYPHASE  AND  SINGLE-PHASE  TRACTION. 

ments  the  power  was  supplied  from  a  300-kw  rotary  converter, 
generating  at  25  cycles  and  located  in  a  combined  water  and  steam- 


FlQ.   5. —  MAP  SHOWING  RELATIVE  GEOGRAPHICAL  LOCATION  OF  THE  LANSING, 

ST.  JOHNS  &  ST.  Louis  ROAD. 

power  plant  about  two  miles  from  the  Lansing  end  of  the  line. 
The  energy  was  carried  to  the  motor  over  two  No.  3  bare  copper 


ARNOLD:     POLYPHASE  AND  SINGLE-PHASE  TRACTION.       2!) 

wires,  one  of  which  was  attached  to  the  rails  of  the  track  and  the 
other  to  the  No.  .00  trolley  wire.  Much  experimental  work  had  been 
done  at  the  shops  where  the  machine  was  constructed  during  the 
preceding  year. 

On  June  15,  1903,  two  trips  were  made,  each  about  three  miles 
long,  with  the  first  experimental  machine,  which  is  illustrated  in 
Fig.  6. 

On  the  first  trip  eight  persons1  were  carried  and  on  the  second 
trip  132  persons  were  aboard,  and  I  give  the  names,  as  I  believe 
this  was  the  first  public  demonstration  of  a  single-phase  railway 
built  for  commercial  use.  At  this  time  the  voltage  on  the  over- 
head conductor  was  carried  at  2400  volts. 

The  locomotive  was  a  crude  affair  made  hastily  from  a  truck  of 
one  of  the  cars  (Fig.  7)  upon  which  was  placed  the  motor,  some 
rough  timber  for  supporting  the  transformers,  and  the  air  tanks 
and  controlling  devices  originally  planned  to  be  placed  on  a  large 
car  as  shown  in  Figs.  8  and  9,  but  which  a  single  motor  was  unable 


FIG.  8. —  DRAWING  OP  CAB  OF  LANSING,  ST.  JOHNS  &  ST.  Louis  ELECTRIC 

RAILWAY. 

to  drive,  thus  necessitating  the  temporary  construction  shown  in 
Fig.  6. 

The  above  tests  demonstrated  that  the  motor  would  work,  and  as 
the  first  machine  was  necessarily  a  makeshift  and  had  been  con- 
siderably damaged  during  its  preliminary  trials,  it  was  thought 
bost  not  to  attempt  -further  tests  until  a  complete  equipment  could 
be  built. 

1.  A.  S.  Courtright,  G.  A.  Damon,  W.  A.  Blanck,  J.  F.  Scott,  T.  M. 
Keeley,  Fred  Rider,  M.  P.  Otis  and  B.  J.  Arnold. 

2.  Mr.  and  Mrs.  A.  S.  Courtright,  Paul  Courtright,  Mr.  and  Mrs.  T.  M. 
Keeley,  Leroy  Keeley,  Mr.  and  Mrs.  Fred  Rider,  Mrs.  T.  E.  Hamilton,  Mrs. 
A.  N.  Hamilton,  Miss  Isabel  Hamilton,  H.  B.  Quick  and  M.  P.  Otis. 


30       ARNOLD:     POLYPHASE  AND  SINGLE-PHASE  TRACTION. 

A  new  double-motor  equipment  in  the  form  of  a  locomotive, 

illustrated  in  Figs.  10  and  11,  was  completed  and  made  ready 

I 


FlG.    10. LONQITUDIONAL   SECTION   OF  LOCOMOTIVE  NO.  2. 

for  operation  early  in  December,  1903,  but  on  the  morning  of 
Dec.  18,  a  few  days  prior  to  the  date  set  for  public  tests,  the 
carhouse  in  which  it  was  stored  was  completely  destroyed  by  fire 


ARNOLD:     POLYPHASE  AND  SINGLE-PHASE  TRACTION.       31 

and  with  it  went  the  locomotive,  two  new  cars  built  for  the  system, 
and  a  steam  locomotive  used  on  the  line. 


FIG.  11. —  TBANSVEBSE  SECTION  OF  LOCOMOTIVE  wo.  2. 


32       ARNOLD:     POLYPHASE  AND  SINGLE-PHASE  TRACTION. 

Unfortunately  no  photographs  were  secured  of  the  complete 
machine  before  it  was  destroyed,  but  Fig.  12  shows  the  wreck  the 
morning  after  the  fire,  and  Fig.  13  shows  the  character  of  the 
weather  and  the  conditions  of  the  road  at  the  time. 

No  insurance  was  carried  upon  the  machine,  but  the  work  of 
rebuilding  was  at  once  commenced.  All  of  the  electrical  machin- 
ery and  other  electrical  parts  were  returned  to  the  manufacturers 
to  be  rewound  or  rebuilt,  and  all  parts  of  the  air  machinery  that 
could  not  be  repaired  on  the  ground  were  ordered  new,  except  the 
main  cylinder  castings,  which  though  cracked  were  in  such  a  con- 
dition as  to  warrant  attempting  their  repair  by  pumping  a  strong 
solution  of  sal  ammoniac  and  water  into  them  under  pressure  and 
thus  attempting  to  close  the  cracks  by  oxidization.  This  was 
partially  successful,  and  a  new  locomotive,  Figs.  14  and  15, 
christened  "Phoenix"  was  completely  and  recently  made  ready 
for  trial. 

In  the  meantime,  as  it  became  necessary  to  place  the  road  in 
operation  electrically  in  order  to  operate  in  conjunction  with  the 
local  street  railway  system  in  the  city  of  Lansing,  which  had  been 
acquired  by  the  owners  of  the  Lansing,  St.  Johns  &  St.  Louis  line, 
provision  for  operating  the  direct-current  motor  cars  of  the  city 
line  was  made,  under  my  direction,  by  adding  additional  copper 
and  the  installation  of  a  rotary  sub-station. 

It  is  interesting  to  know  that  the  rotaries  and  sub-station  appara- 
tus now  operating  this  road  are  the  same  ones  installed  on  the 
Chicago  &  Milwaukee  Electric  Eailway  in  1899,  they  having  served 
their  purpose  well  and  been  removed  to  make  room  for  larger  ones 
recently  installed  to  take  care  of  the  increased  demands  of  that 
road. 

The  Lansing,  St.  Johns  &  St.  Louis  road  is  now  so  equipped  that 
by  throwing  suitable  switches  in  the  sub-station,  either  direct  cur- 
rent at  600  volts,  or  alternating  current  at  6000  volts,  can  be 
turned  on  the  trolley-wire  at  will,  thus  making  it  practicable  for 
the  road  to  run  direct-current  cars  a  large  part  of  the  time,  and 
allow  the  operation  of  my  experimental  locomotive  at  such  times 
as  may  be  desired. 

On  the  evening  of  Aug.  3,  1904,  the  Phoenix  made  its  trial 
run  from  Lansing  to  Dewitt,  a  distance  of  eight  miles,  carry- 
ing the  superintendent  of  the  road,  two  newspaper  men,  the  writer 
and  three  assistants. 


ARNOLD:    POLYPHASE  AND  SINGLE-PHASE  TRACTION.       33 


FIG.  16. —  DETAILS  OF  OVERHEAD  WORK,  USED  ON  LANSING.  ST.  JOHNS  &  ST. 
ELEC.  BYS. —  3.  LOUIS  RAILWAY. 


34      ARNOLD:     POLYPHASE  AND  SINGLE-PHASE  TRACTION. 


Trouble  in  the  power-house,  due  to  the  breaking  of  an  engine 
prior  to  the  trial,  made  it  impossible  to  maintain  the  current  on  the 
line  continually,  on  account  of  the  blowing  of  the  circuit  breaker; 
otherwise  the  run  would  have  been  made  over  the  entire  20  miles 
to  St.  Johns.  The  run  was  made  with  6000  volts  on  the  trolley- 
wire,  and  on  the  whole  was  satisfactory,  as  it  demonstrated  the 
ability  of  the  machine  to  run  smoothly  at  all  speeds  from  zero 
to  synchronous  speed,  and  maintain  a  constant  load  on  the  power- 
house. The  control  of  the  speed  of  the  car  seemed  perfect. 

Owing  to  the  cracks  in  the  cylinder  castings  not  having  been 
fully  stopped,  and  loss  of  current  from  the  absence  of  several  in- 
sulators on  the  line,  no  attempt  to  determine  efficiency  of  opera- 
tion was  made,  but  as  these  defects  can  be  remedied  additional 


FlQ.    17. —  VIEWS   OF   SPECIAL  INSULATOR   USED   FOB  BUPPOBTINQ   THE  WOBK- 

INQ  CONDUCTOR. 

run&  will  be  made  to  determine  the  efficiency  of  the  system.  This 
is,  I  believe,  the  longest  run  yet  made  upon  a  road  built  for  single- 
phase  operation. 

Having  thus  described  the  conditions  surrounding  the  develop- 
ment and  application  of  the  system,  a  more  detailed  description  of 
it  may  be  of  interest. 

The  track  of  the  road  does  not  differ  from  standard  steam  or 
electric  railroad  construction,  except  that  but  one  line  of  rails 
was  bonded,  as  it  was  thought  that  at  the  high-working  voltage  the 
amount  of  current  would  be  so  small  that  the  bonding  of  the  other 
rail  would  be  unnecessary. 

"Wood  was  used  for  both  pole  and  bracket,  as  illustrated  in 
Fig.  16,  which  also  shows  the  details  of  construction  of  the  over- 
head work.  A  special  trolley  insulator  was  designed,  Fig.  17,  as 


ARNOLD:     POLYPHASE  AND  SINGLE-PHASE  TRACTION.       33 

it  was  intended  to  experiment  with  pressures  as  high  as  15,000 
volts  on  the  working  conductor.  The  insulators  were  made  of 
annealed  glass  and  tested  up  to  30,000  volts. 

Had  a  bow  or  some  form  of  sliding  contact  been  used  as  originally 
intended,  these  insulators  would  probably  have  proven  satisfactory ; 
but  with  the  running  of  short  four-wheeled  direct-current  cars 
over  the  line  came  the  frequent  jumping  off  of  the  trolley  wheels, 
resulting  in  the  breaking  of  many  of  the  insulators.  Such  con- 
struction should,  therefore,  not  be  used  with  anything  but  a  slid- 
ing contact  or  bow  trolley. 

One  of  the  most  difficult  problems  in  the  development  of  the 
electropneumatic  system  was  to  design  an  air  compressor  which 
would  not  only  work  efficiently  as  a  compressor  but  could  also  be 
made  to  work  efficiently  as  an  engine.  Much  time  was  spent 
upon  the  development  of  various  valve  mechanisms  and  many  types 
of  engines  were  designed.  The  objects  to  attain  were  first,  quick- 
opening  and  quick-closing  valves;  and  second,  valves  so  driven 
that  when  the  machine  was  not  running  as  an  engine  they  would 
not  be  mechanically  moved.  They  should  also  be  capable  of  oper- 
ating automatically  when  the  machine  is  running  as  a  compressor. 
By  the  development  of  electropneumatically  operated  valves, 
described  later,  these  objects  were  accomplished,  and  the  inequality 
of  the  point  of  cut-off,  due  to  what  is  technically  known  as  "the 
angularity  of  the  connecting  rod  "  was  eliminated,  thus  making  it 
possible  for  each  compressor  when  running  as  an  engine  to  open  its 
inlet  and  outlet  valves  at  exactly  the  right  point  of  cut-off  for  each 
end  of  the  cylinder  under  all  conditions  of  operation,  regardless  of 
the  direction  in  which  the  engine  runs.  This  was  accomplished  by 
the  use  of  valves  which  operate  pneumatically  without  loss  of  air, 
the  time  of  opening  and  closing  being  electrically  piloted  by  means 
of  collector  rings  mounted  upon  or  driven  by  the  main  shaft  of 
the  engine.  These  collector  rings  consist  of  several  insulated  seg- 
ments so  placed  with  reference  to  the  crank  that  they  operate 
the  valves  instantaneously  at  such  times  as  an  eccentric  would  if 
it  were  placed  directly  in  line  with  or  directly  opposite  the  crank 
pin. 

Primarily  a  car-motor  equipment  consists  of  a  single-phase  motor 
having  both  its  rotor  and  its  stator  free  to  revolve  (Figs.  18  and  19), 
each  of  which  is  attached  to  an  air  compressor  in  such  a  manner 
that  when  it  revolves  its  compressor  will  be  driven  or  either  air 
compressors  may  at  times  become  an  air  engine  and  drive  the  part 


H6       ARNOLD:     POLYPHASE  AND  SINGLE-PHASE  TRACTION. 

of  the  electric  motor  to  which  it  is  attached.  Fig.  20  shows  the 
bottom  view  and  Fig.  21  the  top  view  of  the  combined  electro- 
pneumatic  motor  standing  on  end  in  the  shop  prior  to  being  placed 
upon  the  truck,  and  Figs.  22  and  23  show  the  two  motors  com- 
plete mounted  upon  a  truck.  The  following  description  will 
make  clear  the  application  of  the  principles  and  the  operation 
of  the  different  parts  of  the  system.  Perhaps  I  cannot 
describe  the  theory  and  working  of  the  machine  better  than  by 
employing  language  which  I  have  previously  used,  so  amplified  as 
to  conform  to  the  additional  figures  given  in  this  paper  showing 
more  clearly  the  interior  mechanism  of  the  machine. 

Fig.  24  represents  diagrammatically  the  working  parts  of  the 


Fio.  £4. —  DIAGRAMMATIC  ARRANGEMENT  OF  ELECTRO-PNEUMATIC  MOTOR. 

system  when  a  reciprocating  type  of  air  compressor  is  used. 
Fig.  25  shows  a  transverse  section  through  the  air  cylinders,  the 
regulating  valves  and  the  individual  cylinder  valves  of  the  machine 
shown  in  Figs.  22  and  23. 

The  rotor  R,  Fig.  24,  is  geared  to  the  axle  of  the  car,  and  by 
means  of  crank  pin  <7',  secured  in  pinion  Pf  also  drives  the  com- 
pressor cylinder  R  C,  while  the  stator  8  is  free  to  revolve  around 
the  rotor  and  drive  by  means  of  crank-pin  C  the  compressor  cylinder 
8  C.  Both  cylinders  are  piped  to  air  reservoirs  located  under  the 
car,  and  are  also  provided  with  suitable  valves,  A,  B,  C  and  C' , 
shown  in  Fig.  25,  which  in  connection  with  the  pneumatically 
operated  cylinder  valves  previously  mentioned,  are  manipulated 


ARNOLD:    POLYPHASE  AND  SINGLE-PHASE  TRACTION.     37 


3S       ARNOLD:     POLYPHASE  AND  SINGLE-PHASE  TRACT10X. 

from  the  controller  in  such  a  manner  as  to  make  them  perform 
their  various  functions.  Thus  the  entire  regulation  of  the  speed 
of  the  car  is  controlled  by  the  air  cylinders. 

For  the  purpose  of  making  clear  the  different  operations  of  the 
system,  Fig.  26,  showing  a  speed  diagram,  has  heen  prepared,  in 
which  on  the  axis  of  abscissae  0  D  L  are  represented  the  different 
car  speeds  in  per  cent  of  the  synchronous  motor  speed,  and  the  co- 
ordinate axis  A  0  B  represents  the  rotor  and  stator  speeds  cor- 
responding to  the  car  speeds  shown  on  axis  0  D  L.  The  operation 
of  the  car  may  be  divided  into  the  following  periods : 

1.  Standing  in  the  Station. 

In  Fig.  24,  the  rotor  R  being  rigidly  geared  to  the  car  axle  is 
now  standing  still,  while  the  stator  8  runs  with  full  synchronous 
speed,  and  is  thus  transferring  the  full  energy  of  the  electric  motor 
through  crank  C  to  the  compresser  cylinder  S  C,  which  energy  is 
being  delivered  in  the  form  of  compressed  air  into  the  air  reservoir. 
Since  the  relative  velocity  between  the  stator  and  the  rotor  is  con- 
stant under  all  conditions  of  operation,  the  speed  curves  of  stator 
and  rotor  may  be  represented  by  two  parallel  lines,  OCR  and 
A  D  S,  shown  in  Fig.  26.  The  origin  0  of  the  given  co-ordinate 
system  represents  the  period  of  rest  of  the  car,  and,  therefore,  indi- 
cates zero  rotor  speed  and  full  stator  speed  in  a  negative  or  down- 
ward direction,  as  the  stator  is  now  revolving  in  an  opposite  direc- 
tion from  that  which  the  rotor  must  revolve  to  drive  the  car  for- 
ward. If  it  is  assumed  that  0  A  equals  the  active  torque  of  the 
stator,  then  0  B,  which  equals  0  A,  will  represent  the  reactive 
torque  of  the  rotor  exerted  on  the  car  axle,  so  that  if  the  car  is 
free  to  move  the  reactive  torque  can  be  used  for  starting  and 
accelerating  the  car. 

When  the  car  is  standing  in  the  station  it  is  held  at  rest  by  placing 
valve  B  (Fig.  25)  by  means  of  the  controller,  in  the  position  shown 
ir.  full  lines,  thus  allowing  air  from  the  storage  tanks  to  enter 
through  opening  Q  in  the  direction  of  the  arrow  R  to  passage  ZT, 
which  is  in  communication  with  the  high-pressure  valves  of  the 
rotor  cylinder.  The  pressure  may  be  thus  increased  behind  the 
rotor  piston  to  such  an  extent  that  it  overcomes  the  effort  of  the 
rotor  to  revolve,  thus  tending  to  cause  the  stator  to  revolve,  while 
at  the  same  time  it  holds  the  car  at  rest  without  the  use  of  wheel- 
brake?.  When  the  car  is  standing,  the  stator  is  running  at  full 


ARNOLD:     POLYPHASE  AND  SINGLE.-PHASE  TRACTION.       39 

synchronous  speed  and  the  stator  cylinder  is  drawing  in  cold  air 
through  opening  D  in  the  direction  of  arrow  0,  which  enters  the 
stator  cylinder  through  the  inlet  valves  shown  at  the  top  of  the 
cylinder.  The  air  is  delivered  from  the  stator  cylinder  through  the 
outlet  valves  into  passage  H,  and  may  be  delivered  in  the  direction 
of  arrow  R  into  opening  Q  and  thence  to  the  storage  tanks  or  into 
the  passage  H'  for  the  purpose  of  holding  the  rotor  cylinder  still 
or  supplying  it  with  air  in  starting. 

2    Starting  and  Accelerating. 

To  start  the  car  the  air  cushion  behind  the  piston  of  rotor 
cylinder  R  C,  Fig.  24,  is  removed  by  so  manipulating  the  controller 
that  the  exhaust  valves  shown  at  the  top  of  Fig.  25  are  opened; 


Fio.  26. —  DIAGRAMMATIC  REPRESENTATION  OF  OPERATION  OF  ELECTRO-PNEU- 
MATIC MOTOR. 

the  air  which  is  being  compressed  by  the  stator  cylinder  is  then 
delivered  from  passage  H  into  H' ,  as  indicated  by  the  arrow  R, 
supplemented  by  the  stored  air  from  the  tanks.  The  controller  is 
now  set  at  the  position  of  maximum  cut-off  for  the  inlet  valves  of 
the  rotor  cylinder,  shown  at  the  bottom  of  Fig.  25. 

The  rotor  then  begins  to  revolve  and  as  it  accelerates  the  stator 
slows  down  by  exactly  the  same  amount  that  the  rotor  has  increased 
its  speed;  as  the  rotor  and  car  speed  increase  the  controller  is 
gradually  moved  so  that  the  inlet  valves  of  the  rotor  cylinder  give 
a  smaller  percentage  of  cut-off  until  the  car  speed  corresponds  to 
the  full  synchronous  speed  of  the  motor,  at  which  time  the  stator 


40       ARNOLD:     POLYPHASE  AND  SINGLE-PHASE  TRACTION. 

comes  to  rest.  During  this  period  of  acceleration  the  air  compressed 
by  the  stator  cylinder,  instead  of  being  delivered  to  the  tanks  to 
lose  its  heat,  is  delivered,  hot,  directly  to  the  rotor  cylinder  through 
the  passages  H  and  H' ,  either  directly,  as  indicated  by  arrow  Rf  in 
case  the  valve  A  is  placed  as  shown  in  full  lines,  or  through  the 
automatic  valve  (7,  as  indicated  by  arrow  S,  thence  through  a  pas- 
sage (not  shown)  communicating  with  opening  Q.  In  the  latter 
case  the  valve  A  is  placed  in  position  A'.  The  valve  G,  known  as 
the  stator  automatic  valve,  is  provided  with  a  spring  so  set  that  it 
maintains  a  constant  pressure  in  passage  H  and  hence  a  constant 
load  upon  the  electric  motor. 

After  the  air  thus  delivered  from  the  stator  cylinder  has  done 
its  work  behind  the  rotor  piston,  it  is  exhausted  cold,  owing  to  the 
rapid  expansion,  into  the  passage  L'f  and  thence  in  the  direction  of 
the  arrow  N  into  the  passage  L  leading  to  the  inlet  valves  of  the 
stator  cylinder.  Thus  a  complete  cycle  is  established  and  the  same 
air  may  be  used  repeatedly  if  the  rate  of  acceleration  is  such  that 
the  rotor  cylinder  uses  all  of  the  air  supplied  by  the  stator  cylinder 
and  under  these  conditions  no  exhaust  to  the  atmosphere  from  the 
rotor  cylinder  will  take  place.  Since  all  of  the  air  passages  and  both 
cylinders  are  enclosed  in  a  water-jacket,  the  heat  generated  while 
compressing  is  delivered  to  the  water  and  extracted  by  the  rotor 
cylinder  when  working  as  an  engine,  the  water  performing  the 
double  function  of  cooling  the  air  during  compression  and  reheat- 
ing it  during  the  process  of  expansion,  thus  increasing  the  efficiency 
of  the  combination.  Tests  already  made  indicate  that  this  jacket- 
ing water  will  remain  at  a  fairly  constant  and  comparatively  low 
temperature. 

Opening  D  is  known  as  the  cold-air  inlet  and  the  exhaust  out- 
let. It  is  provided  with  a  valve  acting  against  a  spring  which  nor- 
mally keeps  opening  D  closed  to  the  outside  air.  In  case  the  volume 
of  air  required  by  the  stator  cylinder  is  greater  than  the  amount 
exhausted  from  the  rotor  cylinder,  this  valve  automatically  opens 
and  permits  the  outside  air  to  enter  the  passage  L  through  the  open- 
ing D,  as  indicated  by  the  arrow  0.  This  valve  also  opens  auto- 
matically to  admit  air  to  the  rotor  cylinder  in  the  direction  of  the 
arrow  P  at  such  times,  hereinafter  described,  as  it  may  be  compress- 
ing air.  The  valve  is  also  electrically  controlled  in  such  a  manner 
that  it  can  be  opened  by  the  motorman  when  it  is  desired  to  operate 
the  car  as  an  independent  unit  with  air  alone  by  means  of  the 
rotor  cylinders  acting  as  engines. 


ARNOLD:     POLYPHASE  AND  SINGLE-PHASE  TRACTION.      41 

Kef  erring  to  Fig.  26,  which  graphically  represents  the  period  of 
acceleration,  since  the  electric  motor  always  runs  at  a  constant  speed 
and  constant  load,  it  has  a  constant  torque,  and,  therefore,  the 
vertical  distance  0  A  between  ADS  and  OCR  may  be  considered 
as  representing  the  energy  delivered  by  the  electric  motor.  The 
length  of  any  ordinate  extending  from  0  D  to  0  C  represents  the 
proportionate  amount  of  energy  derived  from  the  electric  motor 
which  is  applied  directly  through  pinion  P  and  gear  Gf  Fig.  24, 
to  the  propulsion  of  the  car  wheel.  The  corresponding  ordinate 
extending  below  0  D  to  S  D  represents  the  proportionate  amount 
of  the  energy  of  the  electric  motor  which  is  absorbed  in  compressing 
air  through  the  cylinder  S  C,  which  energy,  in  the  form  of  air,  is 
immediately  transferred  to  cylinder,  the  R  (7,  and  is  utilized  in  accel- 
erating the  car.  In  practice,  however,  since  there  will  be  some  loss 
IL  transferring  the  energy  from  electrical  energy  to  energy  in  the 
form  of  compressed  air  and  back  again  into  mechanical  energy,  the 
energy  thus  lost,  whatever  it  may  be,  must  be  drawn  from  the  stor- 
age tanks  and  the  requisite  amount  of  air  from  these  tanks  sup- 
plied to  the  rotor  cylinder  R  C  in  order  to  maintain  the  full  power 
of  the  electric  motor  upon  the  car  axle  during  the  period  of  accelera- 
tion. 

Should  it  be  desired  to  accelerate  at  a  greater  rate  than  the  full 
power  the  electric  motor  is  capable  of  giving  to  the  car,  the  ad- 
ditional energy  may  be  supplied  in  the  form  of  air  from  the  stor- 
age tanks  through  the  rotor  cylinder,  thus  increasing  the  total 
energy  given  to  the  car  during  acceleration,  in  which  case  this  total 
power  would  be  represented  for  any  given  instant  by  a  point  above 
line  B  C. 

The  air  thus  drawn  from  the  tanks  enters  through  the  opening 
Q  and  flows  in  the  direction  of  arrow  R  into  the  passage  H',  and 
thence  to  the  rotor  cylinder. 

8    Running  Speeds. 

Assuming  that  during  the  accelerating  period  valve  A  has  been  in 
position  A'f  the  air  from  the  stator  cylinder  has  been  delivered 
through  the  stator  automatic  C,  and  a  constant  load  has  been  main- 
tained upon  the  motor.  As  soon  as  the  car  by  the  previous  processes 
reached  a  speed  corresponding  to  the  synchronous  speed  of  the 
motor,  the  exhaust  valves  of  rotor  cylinder  R  C  are  held  open  by 
setting  the  controller  at  a  suitable  position  and  the  piston  of  the 
rotor  cylinder  now  runs  free.  The  electric  motor  now  gives  its 


42       ARNOLD:     POLYPHASE  AND  SINGLE-PHASE  TRACTION. 

full  power  to  the  car  axle  and  the  stator  and  its  air  mechanism 
remain  at  rest  as  long  as  the  car  runs  at  the  speed  corresponding 
to  the  synchronous  speed  of  the  motor.  Since  the  pressure  behind 
the  piston  of  the  stator  cylinder  is  maintained  constant  by  the 
valve  Cf  the  stator  will  remain  at  rest  only  so  long  as  the  resistance 
offered  by  the  car  is  exactly  equal  to  the  power  of  the  electric  motor. 
In  case  this  resistance  is  less  than  the  capacity  of  the  electric  motor, 
the  stator  cylinder  will  automatically  reverse  and  begin  to  rotate 
ir  the  same  direction  as  the  rotor  is  running,  and  slowly  compress 
air  and  deliver  it  to  the  storage  reservoir.  In  case  the  resistance 
of  the  car  is  greater  than  the  capacity  of  the  motor,  the  speed  will 
decrease  and  the  stator  automatically  reverse  and  run  in  an  opposite 
direction  from  that  of  the  rotor,  and  will  then  be  operating  in  the 
same  manner  as  during  the  accelerating  period.  It  will  thus  be 
seen  that  no  attention  need  be  paid  to  the  stator  during  the  running 
period,  for  it  automatically  takes  care  of  itself. 

When  the  resistance  of  the  car  is  greater  than  the  capacity  of 
the  electric  motor,  speeds  above  synchronism  can  be  maintained 
only  by  supplying  the  rotor  cylinders  with  stored  air  from  the 
tanks,  and  can  only  be  maintained  for  short  distances,  or  until  the 
storage  capacity  of  the  air  reservoirs  is  exhausted. 

The  distance  from  the  line  0  D  L  to  that  portion  of  the  line 
ADS  above  0  D  L  in  Fig.  26  represents,  at  any  given  speed,  the 
proportionate  amount  of  energy  which  must  come  from  the  tanks 
and  be  supplied  through  cylinder  S  C.  The  distance  from  D  L  to 
C  R  represents  the  total  energy  given  to  the  car  by  the  combined 
action  of  the  electric  motor  and  stator  cylinder. 

4    Retardation. 

To  bring  the  car  to  rest,  instead  of  applying  mechanical  brakes 
to  the  wheels  in  the  ordinary  manner,  thereby  dissipating  the  entire 
stored  energy  of  the  car  in  the  form  of  heat,  this  energy  is  saved 
in  the  form  of  compressed  air  to  assist  in  starting  the  car,  by  set- 
ting the  controller  in  such  a  position  that  the  rotor  cylinder  com- 
presses air  and  delivers  it  into  the  storage  tanks.  Any  desired 
rate  of  retardation  can  be  secured  by  throttling  the  delivery  pas- 
sages from  the  rotor  cylinder  by  means  of  valve  B,  Fig.  25,  by  mov- 
ing it  toward  the  direction  indicated  at  B'.  When  the  valve  is  in 
the  position  B'f  the  passage  H'  is  brought  into  communication  with 
the  automatic  valve  C' ,  so  set  that  it  will  release  just  before  the 
slipping  point  of  the  wheels  is  reached.  The  kinetic  energy  of  the 


ARNOLD:     POLYPHASE  AND  SINGLE-PHASE  TRACTION.       43 

car  can  thus  be  all  absorbed  by  means  of  the  rotor  cylinder  and  the 
car  brought  to  rest  without  wheel  brakes,  although  such  brakes 
are  supplied  for  emergency,  but  need  not  be  often  used. 

5.  Reversing. 

When  it  is  desired  to  run  the  car  backward  for  short  distances 
the  electric  motor  is  not  disturbed,  and  the  power  is  furnished  from 
the  rotor  cylinders  acting  as  engines;  but  if  it  is  desired  to  run 
backward  for  any  great  distance,  the  current  is  thrown  off  the 
motor,  the  stator  engine  is  reversed  and  the  stator  is  brought  to 
speed  with  the  air,  when  the  current  is  again  thrown  on  to  the 
motor,  and  the  cycle  of  operation  is  the  same  as  when  running 
forward. 

A  detailed  description  of  the  valves  may  now  be  of  interest: 

DESCRIPTION  OF  VALVES. 

Eef erring  to  Fig.  25,  the  lower  valves  are  termed  the  high-pres- 
sure valves  and  act  as  inlet  valves  when  the  machine  is  running 
us  an  engine  and  as  outlet  valves  when  the  machine  is  running  as 
ji  compressor. 

The  upper  valves  are  the  outlet  or  exhaust  valves  when  the  ma- 
chine is  running  as  an  engine  and  the  inlet  or  admission  valves 
vvhen  the  machine  is  running  as  a  compressor.  Both  valves  are 
shown  in  detail  drawn  to  a  larger  scale  in  Fig.  27. 

In  Fig.  27  (bottom  valve)  part  15-79  is  the  valve  proper  and  is 
of  steel;  it  is  carried  in  a  brass  guiding  case,  15-464,  screwed 
solidly  in  the  retaining  walls  of  the  cylinder.  Into  this  seat  15-464, 
is  screwed  a  brass  guiding  piece,  15-463,  which  serves  the  double 
purpose  of  guiding  the  solenoid  plunger,  15-78,  and  as  a  chamber 
for  the  solenoid  coil  X.  In  the  center  of  the  valve  15-479  is  bored 
a  round,  true  socket  or  port  chamber,  into  which  fits  a  round 
plunger  or  piston,  this  being  an  integral  part  of  the  solenoid  core, 
15-78.  This  core  carries  a  flange,  also  integral  with  it,  against 
which  the  spring  15-80  rests,  the  other  end  of  the  spring  resting 
against  15-463.  Surrounding  the  solenoid  core  15-78,  is  placed 
*  solenoid  coil  X  which,  when  energized,  draws  15-78  downward 
and  with  it  the  piston  which  fits  into  the  port  chamber,  15-79. 

Valve  15-79  is  provided  with  one  or  more  ports,  a,  drilled  into 
its  face  and  terminating  in  the  central  port;  chamber.  It  is  also 
provided  with  radial  ports,  I,  terminating  in  the  port  chamber. 
The  portion  of  the  solenoid  core,  15-78,  which  enters  the  port 
Chamber  is  also  provided  with  channels,  c,  drilled  longitudinally, 


44       ARNOLD:    POLYPE ASE  AND  SINGLE-PHASE  TRACTION. 


r 


ARNOLD:     POLYPHASE  AND  SINGLE-PHASE  TRACTION.       45 

which  are  connected  with  radial  openings  d  and  e.  Under  normal 
conditions  of  operation  the  space  between  walls  /  and  g  is  filled 
with  air. 

Valve  15-78  is  round,  and  the  portion  h  is  slightly  less  in  diameter 
than  portion  jt  the  latter  sliding  air  tight  in  15-464,  so  that  if 
pressure  is  admitted  through  ports  bf  d,  c  and  e,  into  the  chamber 
behind  15-79,  the  pressure  will  act  upon  the  portion  ;  of  the  piston 
or  that  portion  which  has  the  largest  diameter  and  consequently  the 
greatest  area,  and  the  valve  will  be  held  tight  against  its  seat.  The 
operation  of  the  valve  is  then  as  follows : 

When  working  as  an  admission  valve  for  the  engine,  current  is 
sent  through  the  solenoid  coil  X,  which  causes  the  solenoid  core 
15-78  to  be  pulled  downward,  thus  withdrawing  its  upper  portion 
which  fits  into  the  port  chamber,  causing  port  a,  normally  closed 
by  15-78,  to  be  opened,  thus  allowing  the  air  to  flow  from  the  in- 
terior of  portion  /  out  through  ports  ef  c  and  a  into  the  cylinder. 
While  this  air  is  thus  permitted  to  escape  into  a  larger  opening,  it  is 
not  lost  for  it  must  act  upon  the  piston  before  escaping  to  the  at- 
mosphere. Since  portion  h  is  smaller  in  diameter,  and,  therefore, 
of  less  area  than  j,  the  high-pressure  air  surrounding  the  valve  will 
force  15-79  downward,  thus  opening  the  main  port  previously 
closed  by  15-79,  allowing  the  high-pressure  air  to  flow  from  the 
high-pressure  air  chamber  into  the  cylinder.  Port  15-79  will  re- 
main open  as  long  as  current  is  held  upon  the  solenoid  coil  X;  but 
as  soon  as  current  is  turned  off  from  the  solenoid  coil,  spring  15-80 
forces  15-78  upward,  thus  closing  port  a,  and  allowing  air  to  again 
enter  through  ports,  ~b,  d,  c  and  e  into  the  chamber  behind  15-79, 
which  forces  it  upward  to  its  seat  on  account  of  the  larger  diameter 
and  consequently  larger  area  of  portion  /.  By  sending  current 
through  the  solenoid  coil  at  suitable  intervals  by  means  of  the  col- 
lector rings  previously  referred  to,  the  valve  can  be  made  to  open 
and  close  and  act  as  an  admission  valve  when  the  machine  is 
operating  as  an  engine,  using  air  for  its  driving  power  and  utilizing 
the  air  to  be  used  in  the  cylinder  of  the  engine  afterward.  The 
solenoid  feature  of  the  valve,  therefore,  acts  only  as  a  pilot  and 
requires  but  little  energy,  which  can  be  supplied  from  the  line  or 
from  any  secondary  source,  such  as  a  small  motor-generator  or  a 
storage  battery. 

When  acting  as  an  outlet  valve  for  the  compressor,  no  current 
is  sent  through  the  solenoid  coil,  and  15-78  is  held  in  its  upward 
position  by  the  spring  15-80,  thus,  as  before,  admitting  high-pres- 


46       ARNOLD:     POLYPHASE  AND  SINGLE-PHASE  TRACTION. 

sure  air  through  ports  5,  d,  o  and  ef  behind  portion  j  of  15-79,  the 
air  thus  supplementing  spring  15-80  to  hold  15-79  against  its 
seat.  The  valve  will  thus  operate  automatically  like  the  outlet  valve 
of  an  ordinary  air  compressor  whenever  the  pressure  in  the  cylinder 
is  sufficiently  great  to  overcome  the  combined  action  of  spring  15- 
80  and  the  air  pressure  behind  15-79. 

Kef  err  ing  now  to  the  upper  or  low  pressure  valve,  Fig.  27,  part 
15-466  is  a  brass  seat  normally  screwed  into  the  casting  of  the 
cylinder.  In  the  drawing  these  valves  on  the  stator  cylinder  are 
shown  screwed  at  their  bases  into  brass  bushes  which  have  nothing 
to  do  with  the  valves,  but  were  used  on  the  stator  side  on  account 
of  a  mechanical  defect  in  the  stator  cylinder  casting. 

As  in  the  case  of  the  high-pressure  valves,  part  15-467  is  a 
brass  seat  screwed  into  the  cylinder  casting,  and  screwed  on  it  for 
mechanical  protection  of  the  solenoid  coil  is  a  cast-iron  part  15-460. 
On  the  interior  of  15-467  fits  piston  15-81,  which  is  screwed  on  to 
valve  seat  15-83,  thus  making  parts  15-81  and  15-83  practically 
integral  so  far  as  operation  is  concerned,  they  having  been  made 
in  different  parts  only  for  convenience  in  assembling. 

Part  15-83  is  provided  with  a  round  port  chamber  into  which 
ports  ra  and  n  enter  in  such  a  manner  that  they  can  be  closed  or 
opened  by  plunger  o.  Plunger  o  is  made  of  steel  and  is  firmly 
secured  to  plunger  rod  p  and  provided  with  ports  q  extending 'com- 
pletely through  it.  To  the  upper  portion  of  rod  p  is  attached  the 
solenoid  core  r.  Solenoid  r  and  with  it  rod  p  and  plunger  o  are 
normally  held  in  their  upward  position  by  means  of  spring  15-87 
resting  against  part  s  which  is  screwed  into  part  i,  the  latter  form- 
ing the  path  for  the  lower  part  of  the  magnetic  circuit  created  by 
the  solenoid  coil.  The  chamber  between  walls  u  and  v  is  the  ex- 
haust or  low-pressure  chamber.  The  action  of  the  valve  when  in 
operation  as  an  exhaust  valve  when  the  stator  cylinder  is  operating 
as  an  engine  is  as  follows: 

Spring  15-87  normally  holds  plunger  r  and  with  it  rod  p  and 
plunger  o  in  their  upward  position,  thus  causing  plunger  o  to  close 
the  ports  ra.  When  it  is  desired  to  operate  the  valve,  and  thus 
exhaust  air  from  the  cylinder,  current  is  sent  through  the  solenoid 
coil,  which  causes  plunger  r  to  be  drawn  into  the  solenoid  coil  and 
downward  against  the  resistance  *of  the  spring  15-87,  thus  carry- 
ing the  stem  p  and  plunger  o  to  the  downward  position  and  open- 
ing the  ports  ra  so  that  the  air  behind  the  piston  of  the  stator 
cylinder  can  flow  freely  through  ports  ra  up  through  the  interior 


ARNOLD:     POLYPHASE  AND  SINGLE-PHASE  TRACTION.       47 

of  the  port  chamber  inside  of  15-83  and  enter  the  space  above 
piston  15-81.    As  the  piston  15-81  is  larger  in  area  than  the  valve 


FIG.  28. —  WIRING  DIAGRAM  OF  LOCOMOTIVE  "  PHCENIX." 

15-83,  the  air  thus  admitted  above  the  piston  causes  it  to  press 
downward,  thus  carrying  with  it  and  opening  valve  15-83,  which 


48       ARNOLD:    POLYPHASE  AND  SINGLE-PHASE  TRACTION. 

will  remain  open  and  allow  the  air  to  exhaust  from  the  cylinder 
into  the  exhaust  or  low-pressure  space  so  long  as  current  remains 
upon  the  solenoid  coil.  When  the  valve  is  used  as  an  inlet  valve 
for  the  compressor,  no  current  is  sent  through  the  solenoid  coil  and 


Fte.  20. — LONGITUDINAL  SECTION  OP  LOCOMOTIVE  "PHCENIX." 

the  valve  works  mechanically,  due  to  the  suction  of  the  piston  in 
the  cylinder,  which  draws  valve  15-83  and  piston  15-81  downward 
against  spring  15-84,  the  latter  heing  only  of  sufficient  strength  to 
normally  hold  valve  15-83  against  its  seat.  The  valves  when  used 


ARNOLD:     POLYPHASE  AND  SINGLE-PHASE  TRACTION.      49 

for  the  purpose  of  operating  the  air  cylinders  as  engines  are  con- 
trolled by  means  of  revolving  commutators  and  suitable  circuits 


FIG.  30. —  TRANSVERSE  SECTION  OF  LOCOMOTIVE  "  PHCENIX." 

in  combination  with  the  controller,  all  as  shown  diag:  ainmatically 
in  Fig.  28. 

ELEC.   RYS. 4. 


50       ARNOLD:     POLYPHASE  AND  SINGLE-PHASE  TRACTION. 

Since  it  was  impracticable  for  me  to  get  the  manufacturer  to 
build  a  single-phase  motor  for  my  first  machine  at  the  time  the 
order  was  placed  (January,  1901),  I  was  compelled  to  utilize  the 
parts  of  a  three-phase  motor  and  have  it  built  as  such  in  order  to 
get  it  at  all.  For  this  reason  the  machines  were  built  as  three- 
phase  machines,  and  provision  was  made  in  the  locomotive  for  run- 
ning them  three-phase  when  it  was  desired  to  do  so  during  the 
preliminary  tests  in  the  carhouse. 

The  diagram,  Fig.  28,  therefore,  shows  the  connections  necessary 
for  running  three-phase,  but  all  tests  on  the  line  were  made  run- 
ning single-phase. 

Figs.  29  and  30  show  longitudinal  and  transverse  sections  of 
the  locomotive  "Phoenix/'  outside  views  of  which  are  shown  in 
Figs.  14  and  15. 


FIG.  31. —  ELEVATION  OF  ELECTRO-PNEUMATIC  TEUCK  WHERE  ROTARY  AIR 
MOTORS  ARE  USED. 


This  machine  was  similar  to  "  Number  2,"  the  one  destroyed  by 
fire,  both  being  equipped  with  the  truck  and  motors  shown  in 
Figs.  22  and  23,  the  only  difference  being  in  the  fdrm  of  the  cab, 
the  type  of  the  transformer  and  the  location  of  the  auxiliaries  in 
the  cab.  In  both  cases  the  current  came  from  the  working  con- 
ductor directly  into  the  terminal  on  one  side  of  the  stationary  trans- 
formers while  the  terminal  of  the  other  side  was  grounded. 

The  secondaries  of  the  transformers  led  to  the  collector  rings 
of  the  stator  parts  of  the  motor  and  supplied  current  at  about 
250  volts. 

In  order  to  permit  the  machines  to  operate  as  independent  units 
by  using  air,  each  was  supplied  with  a  motor  generator  and  a  stor- 
'!«re  battery  to  supply  energy  for  operating  the  valves  of  the  engines. 


ARNOLD:    POLYPHASE  AND  SINGLE-PHASE  TRACTION.       r,l 

While  the  development  of  this  system  has  proven  to  be  a  most 
interesting  and  fascinating  field  of  work,  I  regard  the  machine  in 
its  present  form  as  somewhat  complicated  for  coninierciali  'applica- 
tion, for  like  most  all  new  mechanical  problems  the  first  designs 
are  much  more  complicated  than  subsequent  experience  finds 
necessary. 

By  the  development  of  suitable  rotating  air  machinery  the  system 
is  capable  of  great  simplification,  as  by  this  means  all  of  the  above 
mentioned  reciprocating  parts,  valves  with  their  revolving  collector 
rings  and  connections,  together  with  the  motor  generator  and 
battery  disappear.  The  machine  would  then  take  the  form  shown  in 
Fig.  31  and  be  controlled  entirely  by  two  valves  similar  to  those 
shown  at  the  top  of  Fig.  25. 

If  the  motors  then  be  designed  for  the  working  pressure  of  the 
line,  the  transformer  will  also  disappear  from  the  car;  and  as  the 
current  is  not  manipulated  in  controlling  the  speed  of  the  car,  the 
use  of  high-pressure  motors  becomes  practicable. 

What  the  commercial  value  of  the  system  is  will  depend  upon 
the  results  shown  by  future  tests,  and  on  the  relative  merits  of  the 
various  single-phase  systems  that  have  been  developed  since  the 
announcement  of  the  principles  of  this  system  were  made  public 
at  the  Great  Barrington  Convention  of  the  American  Institute  of 
Electrical  Engineers  in  June,  1902. 

Whatever  its  value  may  be  commercially,  I  believe  its  influence 
in  stimulating  others  to  greater  effort  along  new  lines  cannot  be 
denied,  and  that  the  art  of  electric  railroading  is  one  step  nearer 
its  final  solution  than  it  would  be  today  had  my  efforts  not  been 
exerted  in  this  attractive  field  of  achievement  in  which  I  have 
publicly,8  and  often  unsupported,  proclaimed  my  faith  in  the 
ultimate  supremacy  of  the  alternating-current  motor  for  railway 
work. 

3.  See  Transaction*  American  Institute  of  Electrical  Engineers  as  fol- 
lows: Joint  meeting  with  the  British  Institution  of  Electrical  Engineers, 
Paris,  August  16,  1900;  Niagara  Ealls  Convention,  August  24,  1P01;  Great 
Barrington  Convention,  June  19,  1902  :  New  York  Meeting,  Sept.  26,  1902 


ELECTRIC  TRACTION  ON  BRITISH  RAILWAYS, 


BY  PHILIP  DAWSON. 


INTRODUCTORY. 

The  introduction  of  electric  traction  on  British  railways  is  a 
subject  of  great  interest,  but  can  only  be  discussed  very  briefly  in 
this  paper. 

The  position  of  our  railways  is  one  which  is  beginning  to  make 
all  those  connected  with  these  interests  fully  alive  to  the  necessity 
of  improvement,  both  as  regards  increasing  their  freight  and 
passenger  traffic  and  reducing  the  working  expenses.  Owing  to 
the  stringent  regulations  imposed  by  the  Government,  and  the 
very  densely-populated  districts  which  the  railways  traverse,  the 
capitalization  of  English  lines  is  exceedingly  heavy,  as  the  follow- 
ing figures  clearly  show: 

CAPITALIZATION  AND  MILEAGE  OF  EAILWAYS  IN  THE  UNITED 
KINGDOM  IN  1901. 

Debenture  stock £304,577,862 

Preferential  share  capital 310,819,740 

Guaranteed  share  capital 114,293,436 

Ordinary  share  capital 454,379,107 


Total  capitalization £1,184,070,145 


Double  or  more  lines,  length  of  route 12,272  miles. 

Single  line 9,806      " 


Total  length  of  route 22,078  miles. 


The  ever-increasing  taxation,  as  well  as  of  the  competition  which 
the  railway  companies  are  beginning  to  feel  in  consequence  of  the 
rapid,  introduction  of  electric  traction  on  tramways  in  and  around 

[52] 


f  OF  THE 

(    UNIVERSITY   jl 


V 

Ns^ 


OF 


ELECTRIC  TRACTION   ON   BRITISH   RAILWAYS. 


all  the  large  cities  of  Great  Britain,  are  some  of  the  many  reasons 
which,  notwithstanding  the  fact  that  the  total  number  of  passen- 
gers carried,  as  well  as  the  total  merchandise  and  goods  conveyed, 
has  been  more  or  less  steadily  rising,  has  contributed,  as  will  be 
seen  by  the  following  table,  to  reducing  the  percentage  of  net  re- 
ceipts to  total  paid-up  capital: 

SUMMARY  OF  RAILWAY  RESULTS  OF  THE  UNITED  KINGDOM  FROM 

1850  TO  1901. 


Year. 

Total  number  of 
passengers  carried 
(exclusive  of  season 
ticket-holders.) 

Weight  of  goods  and 
minerals  conveyed, 
Tons. 

Percentage  of 
net  receipts  to 
total  paid-up 
capital. 

Percentage  of 
working  expen- 
diture to  gross 
receipts. 

1850 

72  854  422 

1860. 
1870 

163,435,678 
836  545  397 

89,857,719 

4.19 
4  41 

47 

48 

1880. 
1885. 
1890. 
1895. 
1899. 
1900. 
1901. 

603,885,025 
697,213,031 
817,744.046 
929,770,909 
1,106,691,991 
1,142,276,696 
1,172,895,900 

235,305,629 
257,288,454 
808,119,427 
834.230,991 
413,623,025 
424,929,518 
415,593,441 

4.38 
4.02 
4.10 
8.80 
8.61 
8.41 
8.27 

51 
53 
54 
56 
59 
62 
68 

The  question,  therefore,  arises  as  to  what  our  railways  can  do 
in  order  to  increase  the  ratio  of  net  receipts  to  the  total  paid-up 
capital.  In  my  mind  the  answer  is,  that  their  salvation  lies  in 
the  judicious  adoption  of  electric  traction. 

Railways  have  to  deal  with  three  classes  of  traffic.  1).  The 
short-distance,  suburban,  and  interburban  traffic  in  the  neighbor- 
hood of  our  large  towns  and  between  the  large  centers  which,  in 
many  parts  of  England,  lie  so  close  together;  as  for  instance,  such 
cities  as  Bradford,  Leeds,  Halifax,  Blackburn,  and  the  numerous 
towns  on  the  borders  of  Lancashire  and  Yorkshire.  2).  The  long- 
distance, main-line  traffic.  3.)  The  goods  traffic. 

As  regards  the  suburban  and  short-distance  interurban  traffic, 
there  is  no  doubt  that  electric  traction  will  be  a  great  benefit  to 
the  railways,  and  owing  to  the  dense  population  of  this  country 
which  makes  the  building  of  new  roads  expensive  and  difficult, 
and  the  very  extensive  network  of  railways  which  already  exist, 
the  steam  railways  in  Great  Britain  are  in  exceptionally  favorable 
conditions  to  benefit  by  electrification. 

As  regards  long-distance,  main-line  traffic,  there  may  be  indi- 
vidual isolated  cases  where,  after  electric  traction  has  been  intro- 
duced on  suburban  lines  it  may  be  found  advisable  to  extend  it 
to  the  main  lines. 


54  DAWSON:     ELECTRIC  TRACTION  ON  BRITISH  RAILWAYS. 

English  railway  companies  have  progressed  very  considerably 
of  late;  the  track  construction  is  as  good  as  any  to  be  found  in 
the  world,  and  the  locomotives,  signaling  apparatus,  and  rolling 
stock  are,  as  far  as  steam  traction  is  concerned,  beyond  criticism. 
At  the  same  ;tirrie,  as  already  pointed  out,  the  competition  of 
electric  tramways,  and  the  demands  of  the  public  for  increased 
facilities  of  locomotion,  call  for  a  development  on  entirely  new  lines. 
As  trustee  to  many  millions  of  the  public  for  money,  it  is  evident 
that  no  railway  company  can  take  any  action  or  adopt  any  novel 
system  involving  considerable  expenditure,  except  with  the  greatest 
care  and  after  most  thorough  investigation.  Necessarily,  the 
railway  companies  would  prefer  to  be  perfectly  certain  of  the 
results  before  taking  any  important  steps,  and  to  know  what  has 
been  achieved  financially  by  electrification  of  other  lines.  The 
figures  of  the  cost  of  operating,  and  receipts  on  the  tube  lines  and 
on  the  Liverpool  Overhead,  are  very  instructive,  but  at  the  same 
time,  owing  to  the  different  conditions  under  which  they  are  con- 
structed and  operated,  their  results  do  not  necessarily  apply  to 
all  cases.  It  will  be  some  years  yet  before  reliable  information  is 
available  of  the  results  obtained  on  the  Lancashire  and  Yorkshire, 
and  North  Eastern,  and  under  these  circumstances  the  experience 
of  the  Mersey  railway  is  most  useful. 

The  conversion  of  the  Mersey  line  was  taken  in  hand  and  was  in 
progress  during  1902  and  was  completed  in  May  of  last  year,  and, 
therefore,  it  could  hardly  be  said  to  be  in  full  working  order  during 
the  latter  half  of  last  year,  for  which  accounts  were  available. 
Under  these  circumstances  it  is  not  necessary  to  go  into  these 
accounts  in  detail,  but  it  will  be  interesting  to  note  that  the  three 
minutes'  service  adopted  has  caused  their  train  mileage  to  be  in- 
creased from  some  155,000  miles  to  over  401,000  miles  in  six 
months.  That  this  result  was  justified  is  shown  by  the  fact  that 
the  number  of  passengers  has  increased  from  2,844,708  to  4,153,777, 
and  the  results  show  that  the  traffic  was  almost  entirely  made  up 
of  first  and  third-class  passengers,  the  second  class  having  to  be 
greatly  diminished,  as  might  have  been  anticipated. 

The  results  consequent  on  the  electrification  of  the  Milan-Varese 
line  of  the  Mediterranean  Eailway  Company  are  no  less  surprising. 
For  six  months  ended  June,  1903,  the  total  number  of  passengers 
carried  was  2,977,812.  During  the  whole  year  1900,  when  the 
line  was  entirely  operated  by  steam,  the  total  number  of  passengers 
carried  was  2,768,541. 


DAWSON:     ELECTRIC  TRACTION  ON  BRITISH  RAILWAYS.    55 

SUBURBAN  AND  SHORT-DISTANCE  INTERURBAN  TRAFFIC  CON- 
DITIONS. 

The  position  of  railways  with  respect  to  suburban  traffic  varies 
considerably  with  their  location.  In  some  cases  there  has  been 
a  decrease  both  in  the  number  of  passengers  carried  and  in  the 
gross  receipts,  due  in  a  large  measure  to  the  competition  of  paral- 
leling electric  tramways.  In  other  cases  there  has  been  little  or 
no  change,  whilst  in  others  again,  particularly  those  serving  the 
London  suburbs,  the  requirements  of  the  traveling  public  are  so 
great  that  the  steam  railways  have  never  been  able  to  cope  with 
them,  and  consequently  the  presence  of  competing  tramways  has 
not  as  yet  been  seriously  felt. 

The  electrification  of  the  tramways  in  all  the  big  towns,  as 
well  as  the  construction  of  a  large  number  of  so-called  light  rail- 
ways connecting  the  various  towns,  and  the  activity  shown,  both 
by  the  local  authorities  and  private  companies  in  promoting  new 
lines,  is  rapidly  bringing  matters  to  a  crisis.  The  speeds  allowed 
on  tramways  are  consequently  being  increased  and  there  seems 
but  little  doubt  that  on  a  large  portion  of  the  electric  lines  the 
average  speeds  of  from  12  to  15  miles  an  hour  may  be  allowed  at 
no  very  distant  date.  This  increase  in  speed,  as  well  as  the  fre- 
quent service  given  by  electric  tramways,  will  make  them  most 
serious  competitors  to  steam  railways  unless  their  local  time-tables 
are  considerably  modified  and  improved,  both  as  regards  frequency 
and  average  speed,  and  this  will  only  be  rendered  possible  by  the  in- 
troduction of  electric  traction. 

Thus  there  is  an  urgent  need  for  a  revision  of  the  mode  of 
transport  adopted  on  railways,  in  one  case  to  turn  the  ebbing  tide 
to  traffic,  and  in  the  other  to  satisfy  the  claims  of  a  public  anxious 
to  travel  but  unable  to  do  so  because  of  the  congested  state  of  the 
lines.  If  the  railways  allow  competing  lines  to  proceed  unmolested, 
the  problem  will  be  solved  in  a  manner  extremely  detrimental 
to  the  former.  The  congestion  will  steadily  diminish  by  reason 
of  the  traffic  being  diverted  from  the  railways  by  the  opposing 
interests,  which  will  give  the  facilities  so  urgently  needed  at  the 
present  day. 

The  suburban  traffic  of  the  railways  has  been  growing  rapidly 
with  the  suburbs,  and  as  it  is  largely  concentrated  at  certain  sta- 
tions instead  of  being  uniformly  distributed,  it  is  naturally  very 
congested.  The  state  of  affairs  is  further  complicated  by  the  inter- 


56  DAW  SON:     ELECTRIC  TRACTION  ON  BRITISH  RAILWAYS. 

mingling  of  main  line  and  suburban  traffic  in  the  termini,  owing 
to  lack  of  space  which  prevents  their  being  kept  entirely  separated 
as  they  should  be;  and  by  the  delay  due  to  the  impossibility  at 
present  of  getting  in  and  out  of  the  terminal  stations  expeditiously. 

The  electric  tramways,  though  strong  and  healthy,  are  at  present 
a  young  growth,  but  they  are  extending  with  amazing  rapidity  in 
all  directions,  with  the  result  that  they  are  pressing  hard  upon 
the  railways,  even  in  the  matter  of  comparatively  long-distance 
suburban  traffic;  this  is  a  branch  which  is  essentially  a  province 
of  the  railways,  and  one  in  which  they  should  easily  maintain 
their  supremacy  if  they  are  properly  equipped  to  satisfy  the  require- 
ments of  the  situation. 

The  great  need  of  the  railway  companies  in  respect  of  their  local 
traffic  is  both  to  increase  their  service  and  to  improve  their  methods 
generally,  and  there  is  only  one  practical  way  of  doing  this,  viz., 
electrification.  Under  the  present  conditions  it  is  impracticable  to 
increase  the  frequency  of  suburban  trains,  first,  because  of  the  cost 
of  handling  such  an  increase  by  steam  locomotives,  and  secondly, 
because  of  the  mutual  interference  of  the  main  line  and  suburban 
traffic.  In  other  words,  the  lines  are  at  present  being  worked  very 
near  to  the  limit  of  their  capacity  as  far  as  steam  is  concerned. 

In  the  case  of  suburban  trains  the  amount  of  time  occupied  in 
starting  and  stopping  forms  a  very  large  proportion  of  the  whole 
time  spent  on  the  journey,  so  that  a  very  considerable  saving  would 
be  effected  if  this  waste  of  time  could  be  reduced.  At  the  same  time 
it  is  essential  that  this  should  be  supplemented  by  more  efficient 
methods  of  taking  up  and  detraining  passengers,  which  process, 
under  the  present  circumstances,  entails  an  unnecessary  waste  of 
time  at  stations. 

Attempts  have  been  made  in  various  cases  to  avoid  the  electrifica- 
tion of  steam  lines  by  the  adoption  of  special  locomotives  giving 
exceptionally  high  rates  of  acceleration,  but  the  failure  of  these  has 
only  served  to  emphasize  the  necessity  for  electric  traction,  for  by 
that  means  alone  is  it  possible  to  obtain  really  high  rates  of  accelera- 
tion. Experience  has  conclusively  shown  that  the  only  really  satis- 
factory method  of  handling  suburban  traffic  is  by  means  of  electric 
traction,  and  it  is  a  great  pity  that  hitherto  the  question  has  not 
been  faced  with  greater  boldness  by  those  concerned. 

There  are  such  certain  benefits  to  be  derived  from  the  electrifi- 
cation of  steam  suburban  lines  that  the  only  wonder  is  that  more 


DAWSOy:     ELECTRIC  TRACTION  ON  BRITISH  RAILWAYS.    57 

progress  has  not  been  made.  As  already  stated,  the  main  advantage 
is  that  the  use  of  electric  power  by  permitting  very  high  rates  of 
acceleration  enables  the  frequency  and  consequently  the  carrying 
capacity  of  the  service  to  be  largely  increased,  while  at  the  same 
time  the  working  expenses  per  train  mile  are  decreased.  Also  with 
electric  traction  the  delays  due  to  signals  are  of  less  importance, 
owing  to  the  quickness  with  which  an  electric  train  can  get  under 
way.  Over  and  above  the  foregoing,  the  cleanliness  of  electricity  and 
the  consequent  enhanced  comfort  of  the  passengers  is  a  considerable 
factor  in  increasing  the  popularity  of  the  line. 

Not  a  few  railway  companies  have  expressed  their  opinion  that 
they  have  no  objection  to  the  tramways  taking  their  suburban 
traffic.  According  to  them  this  branch  of  the  service  is  both 
costly  to  maintain  and  difficult  to  manage,  and  at  the  same  time 
it  is  not  a  profitable  source  of  revenue,  and  they  appear  to  be 
quite  content  to  drop  it  altogether  and  fall  back  upon  the  lucrative 
main-line  traffic.  There  are,  however,  two  objections  to  this.  In 
the  first  place,  it  is  extremely  doubtful  whether  any  railway  would 
be  allowed  by  the  Government  to  drop  its  suburban  traffic  com- 
pletely. In  the  second  place,  there  is  too  much  capital  tied  up  in 
this  branch  to  render  it  possible  to  dispense  with  it  entirely.  Few 
companies  could  afford  to  let  such  a  large  amount  of  capital  lie 
idle,  and  there  is  no  reason  why  they  should.  In  my  opinion,  there 
is  not  a  single  railway  company  that  could  not  operate  its  suburban 
traffic  in  the  neighborhood  of  most  of  our  large  manufacturing 
towns  at  a  substantial  profit  if  it  were  to  be  electrified,  and  in  most 
cases  the  profit  resulting  therefrom  would  be  more  than  sufficient 
to  pay  the  interest  on  the  necessary  capital  outlay  called  for  by 
the  change  of  motive  power. 

As  soon  as  the  railways  electrify  their  suburban  lines,  they  will 
hold  a  very  strong  position  against  the  attacks  of  competing  tram- 
ways and  light  railways,  since  in  the  matter  of  speed  they  will  have 
all  the  good  points  of  the  tramways,  without  the  disadvantage  of 
having  to  operate  in  crowded  thoroughfares;  the  greater  distance 
between  the  stops  will  naturally  permit  a  far  higher  schedule  speed 
to  be  maintained,  and  the  higher  the  speed  the  railways  are  able  to 
offer  to  the  public,  the  shorter  will  be  the  distance  of  the  journeys 
for  which  the  tramways  will  prove  more  convenient. 

That  there  is  room  for  great  improvement  in  the  railway  service, 
and  that  there  is  a  larger  amount  of  latent  traffic  to  be  secured  pro- 


58  DAW  SON:     ELECTRIC  TRACTION  ON  BRITISH  RAILWAYS. 

vided  the  railway  companies  go  to  work  in  the  proper  way,  is  clearly 
shown  from  the  statistics  giving  the  number  of  times  the  population 
of  the  large  cities  in  Great  Britain  are  carried  annually. 

The  evidence  given  hefore  the  Koyal  Commission  for  London 
Traffic  by  Mr.  Edgar  Harper,  the  statistician  of  the  London  County 
Council,  shows  that  whereas,  in  1867,  the  population  of  London  was 
carried  22.7  times,  in  1901  it  was  carried  128.7  times.  These 
figures  only  deal  with  the  traffic  in  the  London  area,  and  do  not  in- 
clude the  passengers  brought  in  by  suburban  trains. 

It  must  be  noted  that  these  figures  do  not  include  all  the  omnibus 
lines. 

It  is  interesting  to  note  that  the  number  of  journeys  per  head 
of  population  in  London  is  at  present  small  compared  to  that  in 
many  other  large  cities,  as  will  be  seen  by  the  following  figures : 

London,  1901 129  journeys. 

Glasgow,  1901  174       " 

Liverpool,  1901 187        " 

London  (Mr.  Harper's  estimate),  1903 200        " 

Berlin 223        " 

Greater  New  York 320       " 

Facilities  for  traffic  always  create  traffic,  and  as  facilities  are 
improved  traffic  will  not  only  be  actually  but  also  relatively  greater. 
This  is  shown  by  the  following  figures. 


INCREASE  IN  NUMBER  OF  JOURNEYS  PER  HEAD  OF  POPULATION. 

Greater  London.  Greater  New  York. 

1867 23  1860 47 

1870 27  1870 118 

1880 55  1880 182 

1890 92  1890 283 

1900 , 126  1900 320 

1901 129  1903  (estimated) 415 

1903  (estimated)   200 

From  these  figures  it  will  be  seen  that  the  population  of  London 
is  carried  only  half  the  number  of  times  that  the  population  of 
New  York  is. 


DAW  SON:     ELECTRIC  TRACTION  ON  BRITISH  RAILWAYS.     59 

CONDITIONS  TO  BE  FULFILLED  FOR  A  SYSTEM  OP  ELECTRIC  TRAC- 
TION TO  BE  SATISFACTORY. 

There  are  certain  conditions  which  require  to  be  fulfilled  before 
any  system  can  be  considered  capable  of  giving  satisfactory  results, 
and  these  conditions  are  briefly  set  forth  below. 

1).  Should  moving  machinery  be  found  necessary  in  the  trans- 
forming of  sub-stations,  these  stations  must  be  as  few  in  number 
as  possible.  The  apparatus  used  in  sub-stations  should  be  such  as 
to  require  but  little  attendance  and  should  be  efficient  at  all  loads 
and  capable  of  dealing  for  short  periods  with  very  heavy  overloads. 

2).  The  number  of  conductors  required  to  supply  current  to 
trains  should  be  as  few  as  possible,  and  should  be  capable  of  un- 
limited extension,  and  must  not  interfere  with  the  tracks;  hence 
the  use  of  a  third  rail  is  not  possible. 

3).  It  must  be  possible  to  collect  from  a  single  conductor  sufficient 
power  to  haul  one  or  more  fast  trains  in  service  on  the  lines  between 
the  feeding  points  of  the  conductor. 

4).  It  is  very  desirable  that  the  system  should  be  applicable 
to  main  line  as  well  as  suburban  traction,  and  that  it  should 
be  possible  to  utilize  at  least  two  working  pressures  —  a  low 
pressure  where  found  necessary  in  or  near  the  station,  and  a 
higher  pressure  outside. 

5).  The  system  should  be  such  that  the  trains  can  be  operated 
at  any  speed  required,  and  thus  be  capable  of  making  up  lost  time. 

6).  All  controlling  apparatus  must  be  of  the  simplest  character, 
and  such  that  no  skilled  labor  is  necessary  to  operate  the  trains; 
also  there  must  be  no  dangerous  high  pressure  anywhere  accessible 
to  either  railway  officials  or  passengers. 

7).  If  alternating  currents  are  used  it  is  essential  that  the 
power  factor  be  high  and  that  the  motor  be  capable  of  giving  an 
acceleration  equal  to  that  obtained  with  the  best  series-wound  direct- 
current  motors  at  present  in  use. 

8).  In  certain  cases  it  might  be  advantageous  for  the  motor  to 
be  constructed  to  return  current  to  the  line,  but  in  any  case  it  must 
be  constructed  to  reverse  and  to  be  used  for  braking  purposes. 

OVERHEAD  CONDUCTORS. 

The  doubts  that  have  been  expressed  as  to  the  feasibility  of  adopt- 
ing overhead  wires  on  the  lines  where  steam  locomotives  are  run- 
ning, and  the  objections  which  have  been  urged  against  their  use 


QQDAW80N:     ELECTRIC  TRACTION  ON  BRITISH  RAILWAYS. 

on  this  account,  are,  in  my  opinion,  quite  groundless,  and  there  is 
no  reason  to  anticipate  any  trouble  from  this  cause.  The  engineers 
of  the  Valtelina  railway  informed  me  on  the  occasion  of  my  last 
visit  that  they  had  never  experienced  the  slightest  difficulty  in  re- 
spect to  the  two  overhead  3000-volt  conductors  which  have  been  in 
use  for  over  two  years  on  that  line,  in  spite  of  the  fact  that  steam 
locomotives  burning  soft  coal  are  continually  passing  over  the  line, 
and  that  the  aerial  conductors  in  some  places  have  to  pass  through 
tunnels  from  the  roof  of  which  large  quantities  of  water  are  always 
descending. 

The  conditions  I  have  mentioned  as  being  those  with  which  a 
traction  system  has  to  comply  appear  to  be  exceedingly  difficult  to 
fulfil,  and  the  only  system  which  could  possibly  comply  with  the 
conditions  is  a  single-phase  one.  As  long  as  electric  traction  was 
applied  only  to  tramways  or  lines  with  few  or  no  complicated  junc- 
tions, and  on  which  only  electric  trains  operated  and  there  was  no 
steam  service,  the  continuous-current  railway  motor  has  given  per- 
fect satisfaction. 

But  this  type  of  motor  has  its  limitations,  and  the  necessity  for 
dispensing  with  third  rails  and  using  a  single  high-tension  over- 
head conductor,  has  recently  induced  manufacturers  and  directors 
to  investigate  the  question  thoroughly  and  experiment  upon  the 
possibility  of  constructing  a  really  reliable  single-phase  motor. 

As  might  have  been  expected,  as  soon  as  there  was  a  real  demand 
it  was  not  long  before  an  article  was  produced  to  supply  it.  Aided 
by  the  experience  obtained  in  the  design  of  all  types  of  electric 
machinery,  consequent  on  the  enormous  extension  of  the  applications 
of  electricity  that  has  taken  place  during  the  last  few  years,  a  satis- 
factory alternating-current  single-phase  motor  has  now  been  de- 
veloped. 

The  single-phase  motor  at  present  developed  may  be  divided 
into  two  classes,  the  "  series  "  type  which  has  been  investigated  and 
brought  out  in  Europe  by  Dr.  Finzi,  and  in  America  by  Mr.  Lamme, 
and  the  "  repulsion  "  type,  both  in  the  original  form  as  investigated 
many  years  ago  by  Prof.  Elihu  Thomson,  and  the  "  compensated 
repulsion "  form  as  theoretically  studied  and  discussed  by  Mr. 
Latour  in  France,  and  practically  investigated  by  Messrs.  Eichberg 
and  Winter. 

The  restriction  as  to  the  pressure  at  which  it  is  feasible  to  operate 
a  continuous-current  motor  is  a  great  drawback  to  its  employment 
on  electrified  railways,  for  it  means  that  the  sub-stations  must  be 


DAW  SON:     ELECTRIC  TRACTION  ON  BRITISH  RAILWAYS.    61 

placed  close  together.  The  use  of  an  alternating-current  motor 
Introduces  a  considerable  saving  in  the  cost  of  distributing  mains 
and  conductors  on  account  of  the  high  voltage  which  can  be  utilized, 
and  not  only  are  the  sub-stations  fewer  in  number,  but  they  are 
smaller  and  cheaper  in  first  cost,  maintenance,  and  attendance, 
owing  to  the  absence  of  rotating  machinery. 

The  great  advantage  of  the  single-phase  motor  in  dispensing  with 
the  necessity  for  a  third  rail  and  enabling  a  single  small  high-ten- 
sion overhead  conductor  to  be  used  instead  is  further  enhanced  by 
the  fact  that  in  its  operation  the  rheostatic  losses  involved  in  the 
control  of  continuous-current  motors  are  avoided.  An  additional 
gain  in  efficiency  also  results  from  the  better  distributions  of  the 
sub-stations  and  the  decreased  losses  at  these  points  of  distribution, 
whilst  in  some  cases  a  line  voltage  can  be  employed  which  is  suffi- 
cient to  dispense  entirely  with  transformer  sub-stations.  Also 
owing  to  the  increased  efficiency  of  the  whole  system  the  amount  of 
plant  required  at  the  power  station  is  less  than  would  be  the  case 
for  a  similar  direct-current  system. 

A  very  important  point  about  the  single-phase  motor  is  the  fact 
that  it  can  easily  be  adapted  to  operate  upon  direct-current  cir- 
cuits, a  simple  switching  device  being  all  that  is  necessary  to  make 
the  change. 

Besides  the  solutions  mentioned  above,  there  have  been  various 
more  or  less  unpractical  solutions  suggested,  such  as  that  proposed 
by  the  Oerlikon  company  and  now  being  tried  by  them. 

CONDITIONS  TO  BE  FULFILLED  BY  CONDUCTORS  BRINGING  CURRENT 

TO  TRAIN. 

The  conditions  governing  the  type  and  position  of  the  conductor 
from  which  the  motor  cars  or  locomotives  obtain  their  supply  of 
power  in  the  case  of  most  of  the  steam  suburban  railway  systems  of 
Great  Britain  are  very  different  to  those  which  apply  to  ordinary 
tramways,  newly-built  electric  urban  or  suburban  systems. 

On  most  suburban  systems  the  traffic  is  very  dense  and  either 
local  long-distance  passenger,  or  goods'  trains  are  operating  over  the 
lines  for  the  greater  portion  of  the  24  hours  for  six  days  a  week. 
At  many  junctions  the  traffic  is  largely  increased  by  the  numerous 
other  companies  who  use  that  station  and  there  is  but  little  time 
available  for  keeping  in  proper  repair  the  existing  track  rails  and 
points  and  crossings,  which  are  very  congested.  As  things  stand  at 


62  DAWSON:     ELECTRIC  TRACTION  ON  BRITISH  RAILWAYS. 

present  the  tracklayers  have  the  greatest  trouble  in  finding  time 
to  keep, the  permanent  way  in  proper  condition,  and  they  are  greatly 
hindered  in  their  work  owing  to  the  very  frequent  service  of  trains. 

Under  these  conditions,  the  introduction  of  a  third  "  live  "  rail 
is  practically  impossible.  Even  if  it  was  guarded  it  would  consti- 
tute an  additional  and  constant  source  of  danger  to  the  permanent 
way  men  who,  besides  having  to  avoid  the  passing  trains,  would 
also  have  to  keep  clear  of  the  "  live  "  third  rail. 

Furthermore,  it  is  highly  probable  that  a  "  fourth  "  or  return 
rail,  such  as  has  been  adopted  on  the  Metropolitan  district  and 
the  Lancashire  and  Yorkshire,  would  be  found  necessary  in  order 
to  keep  within  the  7-volt  drop  in  the  return  circuit  required  by 
the  Board  of  Trade. 

It  might  be  possible  to  sectionize  the  third  rail,  and  arrange  so 
that  no  portion  of  it  was  alive  except  while  a  train  was  actually 
passing  over  it ;  but  the  necessary  automatic  switches  would  intro- 
duce most  undesirable  additional  complications,  whilst  there  would 
always  be  a  possibility  of  their  failing  to  work  so  that  it  would  not 
do  for  the  men  to  treat  the  rail  as  quite  harmless. 

In  any  case,  with  the  complicated  track  work  existing  at  many 
large  junctions  it  is  probable  that  there  would  be  no  space  available 
to  place  the  third  and  fourth  rail,  owing  to  the  numerous  signal 
wires  and  the  rods  used  to  operate  the  points. 

The  consequences  following  even  a  slight  derailment  would  be 
most  serious  and  the  danger  of  fire  due  to  short-circuits  thus  in- 
curred, would  be  very  great,  not  to  mention  the  danger  of  electric 
shocks  to  passengers  and  the  entire  stoppage  of  the  service  for  a 
considerable  time,  while  the  damage  to  the  third  rail  was  being 
made  good. 

These  considerations  have  led  a  large  number  of  railway  man- 
agers and  engineers  in  the  United  Singdom,  on  the  Continent,  and 
in  America,  to  the  conclusion  that  the  idea  of  using  any  "  live  " 
rail  conductor  installed  at  or  near  the  level  of  the  track  rail  must 
be  discarded. 

The  onty  other  alternative  is  to  employ  an  overhead  conductor. 
From  a  careful  study  of  the  conditions  which  have  to  be  fulfilled,  I 
have  come  to  the  conclusions  embodied  in  the  following: 

1).  The  conductor  must  be  overhead. 

2).  The  conductor  must  be  as  far  as  possible  at  a  uniform  height 
above  the  track  rails  and  have  no  sag. 


DAW  SON:     ELECTRIC  TRACTION  ON  BRITISH  RAILWAYS.     G3 

3).  The  conductor  must  be  supported  in  such  a  way  that  it  is 
practically  impossible  for  it  to  fall  down  on  the  track  and  get  in  the 
way  of  the  train,  even  in  the  event  of  its  breaking. 

4).  The  current  collector  must  be  light  and  require  little  or  no 
attention.  Any  wear  must  take  place  mainly  on  the  collector  and 
not  on  the  overhead  conductor. 

5).  The  collector  must  be  such  that  it  cannot  slip  or  slide  out  of 
contact  with  the  conductor. 

6).  In  the  event  of  the  collector  fouling  any  portion  of  the  over- 
head work,  the  collector  should  give  way  and  not  the  overhead  work. 

7).  The  collector  must  be  cheaply  and  easily  replaceable. 

8).  The  overhead  conductor  must  be  connected  to  safety  devices 
that  will  automatically  cut  it  out  of  circuit  the  instant  any  breakage 
occurs. 

9).  The  insulation  of  the  conductor  and  collector  must  permit 
the  use  of  very  high  pressures,  say,  up  to  10,000  volts. 

I  have  designed  a  form  of  construction  which  I  think  will  meet 
all  requirements  and  which  will  obviate  any  interruption  of  service 
taking  place.  Furthermore,  I  would  propose,  as  far  as  possible,  not 
to  use  steel  and  iron  except  for  poles  or  brackets  and  to  avoid  the 
employment  of  galvanized  wire  or  hooks  in  any  form  or  shape 
whatever.  The  supporting  wires  would  be  stranded  wire,  composed 
of  either  steel  covered  with  an  outer  layer  of  copper  rolled  onto  it, 
or  else  composed  of  phosphor  or  silicon  bronze  wire;  the  main  con- 
ductor from  which  current  would  be  collected  would  be  of  hard- 
drawn  copper  and  of  a  diameter  of  at  least  one-half  inch ;  the  sup- 
ports of  this  wire  should  not  be  more  than  four  feet  apart  and,  there- 
fore, it  would  be  possible  to  hang  this  wire  in  such  a  way  that  to 
all  intents  and  purposes  it  would  be  absolutely  parallel  to  the  track 
rails. 

CURRENT  COLLECTOR. 

The  question  of  the  form  of  current  collector  or  trolleys  to  be 
used  is  one  which  will  have  to  be  most  carefully  considered.  The 
Oerlikon  company's  type  of  trolley  loses  most  of  its  special  ad- 
vantages when  the  conductor  is  suspended  from  above,  over  the 
tracks.  With  the  wire  in  this  position  it  acts  almost  exactly  like 
an  ordinary  sliding  bow,  and  is  in  no  way  superior  to  that  type  of 
collector.  The  chief  merit  of  the  Oerlikon  trolley  lies  in  its  wide 
range  of  movement,  and  in  the  fact  that  it  can  be  arranged  to  make 


04    DAW  SON:     ELECTRIC  TRACTION  ON  BRITISH  RAILWAYS. 

contact  with  the  conductor  either  on  top,  underneath,  or  at  the  side. 
But  necessarily  the.  first  and  last  positions  require  a  special  form 
of  construction  of  the  overhead  work,  and  are  quite  impossible  where 
the  conductor  is  suspended  from  span  wires,  whether  longitudinal 
or  transverse. 

For  main  line  work  where  there  are  no  complicated  crossings  or 
sidings,  it  is  quite  possible  that  the  form  suggested  by  the  Oerlikon 
company  may  be  adopted  with  the  greatest  advantage. 

Bow  trolleys  may  be  divided  into  two  classes,  one  of  which  is  the 
ordinary  scraping  type,  as  used  by  Messrs.  Siemens  &  Halske,  and 
which  is  the  more  common.  With  the  operation  and  construction  of 
this  trolley  I  am  fully  acquainted.  Such  bows  have  been  running 
for  many  years,  the  soft  metal  on  the  top  of  the  bow  which  make 
the  contact  preventing  wear  of  the  trolley  wire.  The  contact  piece 
is  easily  replaceable  when  it  wears  out. 

The  other  type  of  trolley  is  that  designed  and  constructed  by 
Messrs.  Ganz  &  Company  and  used  by  them  on  the  Valtelina  line; 
this  trolley  instead  of  a  scraping  bow  has  a  roller  mounted  on  ball 
bearings.  This  type  is  considerably  more  expensive  than  the  scrap- 
ing trolley  and  I  do  not  see  any  necessity  for  the  additional  com- 
plications introduced  by  the  use  of  a  revolving  roller. 

In  connection  with  trolleys  the  question  may  arise  as  to  whether 
any  difficulty  is  likely  to  be  encountered  from  the  high  speed  at 
which  the  trolleys  will  run  along  over  wire,  but  there  is  no  reason 
to  anticipate  any  trouble  on  that  account.  In  the  experiments 
carried  out  on  the  high-speed  experimental  electric  railway  between 
Berlin  and  Zossen,  the  bow  was  only  pressed  against  the  wire  by  a 
pressure  not  exceeding  from  3  to  4  kgs,  whereas  the  ordinary 
trolley  has  to  be  pressed  against  the  wire  with  a  pressure  between 
four  and  five  times  as  great:  this  smaller  pressure  is  of  course  ad- 
vantageous as  it  reduces  the  wear  and  tear  on  the  trolley  wire  and 
makes  it  possible  to  have  a  much  lighter  trolley  construction  than 
would  otherwise  be  the  case. 

In  my  opinion  a  trolley  of  the  "  scissors  "  type  would  present 
many  advantages.  The  contact  bar  could  be  made  at  least  as  long 
as  the  whole  width  of  the  carriage  and  this  would  allow  considerable 
latitude  in  the  position  of  the  overhead  wire.  In  situations  where 
there  was  not  sufficient  room  for  the  conductor  to  be  suspended 
over  the  center  of  tracks,  it  could  be  diverted  to  one  side,  and 
increased  head  room  thus  be  obtained  by  reason  of  the  curvature 
of  the  top  of  the  carriage.  In  this  way  it  would  be  quite  possible 


DAWSON:     ELECTRIC  TRACTION  ON  BRITISH  RAILWAYS.    6,T 

to  place  the  conductor  at  an  altitude  not  greater  than  the  highest 
point  of  the  carriage  roof,  and  thus  obtain  the  necessary  clearance. 
In  places  where  it  might  be  considered  inadvisable  to  place  a  bare 
conductor  under  very  low  bridges,  this  portion  might  be  made 
"  dead/'  electrical  continuity  being  obtained  by  insulated  cables. 
With  this  arrangement  a  dummy  trolley  wire  would  be  provided  for 
the  trolley  to  run  on  whilst  passing  under  the  bridge. 

There  is  no  reason  to  fear  that  a  "  scraping  "  contact  would  not 
be  satisfactory,  since  there  is  ample  evidence  to  the  contrary. 
Many  years'  experience  with  third-rail  working  has  demonstrated 
that  very  heavy  currents  can  be  collected  in  this  way,  and  with 
the  single-phase  high-tension  system  the  current  per  trolley  would 
be  very  small;  in  fact,  it  would  probably  be  considerably  less  than 
the  amount  which  is  frequently  collected  by  small  trolley  wheels 
in  ordinary  practice. 

ADVANTAGES  OF  ELECTRIC  TRACTION. 

There  are  several  further  advantages  possessed  by  the  modem 
method  of  traction  which  render  it  greatly  superior  to  steam  haul- 
age, quite  apart  from  the  fact  that  the  high  acceleration  demanded 
for  the  proper  operation  of  suburban  traffic  can  only  be  obtained 
from  the  use  of  electric  power. 

In  the  first  place  steam  trains  have  to  carry  their  own  power; 
that  is  to  say,  a  locomotive  must  not  only  be  able  to  haul  a  certain 
weight  of  train,  but  it  must  carry  coal,  and  machinery  to  consume 
that  coal  and  convert  its  heat  energy  into  tractive  energy  "en 
route,"  and  a  steam  locomotive  is  a  most  uneconomical  instrument 
for  transforming  heat  into  work  for  traction  purposes.  All  this 
adds  to  the  weight  of  the  train  and  greatly  increases  the  weight 
to  be  hauled  per  passenger.  In  the  case  of  some  of  the  trains  on 
the  suburban  systems  serving  London,  the  locomotives  weigh  over 
one-third  of  the  total  useful  weight  of  passenger  coaches  hauled. 

In  the  modern  electric  system  the  heavy  locomotive  is  replaced  by 
a  comparatively  light  motor  car,  and  energy  is  generated  under  the 
most  economical  conditions  at  a  certain  power  station  from  which 
it  can  be  transmitted  many  miles  with  but  slight  loss. 

The  wear  and  tear  of  the  permanent  way,  particularly  at  junc- 
tions and  crossings,  would  be  considerably  less  with  electric  trac- 
tion than  with  steam  traction,  as  in  the  former  there  is  not  that 
tendency  to  roll  or  pitch  which  exists  in  the  case  of  steam  loco- 

EIEC.   RYS. 5. 


(>6  DAW  SON:     ELECTRIC  TRACTION  ON  BRITISH  RAILWAYS. 

motives  and  which  is  due  to  the  movement  of  their  reciprocating 
parts. 

Electric  trains  with  two  or  more  motor  cars  on  the  multiple-unit 
system  have  the  great  advantage  of  distributing  the  weight  of  the 
train  more  evenly  over  the  track  and  also  of  permitting  a  smaller 
weight  on  each  driving  axle  than  would  be  the  case  with  a  loco- 
motive, owing  to  the  larger  number  of  driving  axles.  A  steam  loco- 
motive has  to  be  heavy  enough  to  give  sufficient  weight  on  the 
driving  wheels  to  haul  the  heaviest  train  up  the  steepest  gradient. 
at  the  highest  required  speed.  This  concentration  of  the  weight  is 
very  detrimental  to  the  track,  and  the  bad  effects  are  accentuated 
by  the  pounding  action  caused  by  the  reciprocating  motion  of  the 
engine. 

For  the  same  weight  on  the  driving  wheels  an  electric  motor  can 
exert  a  much  greater  tractive  effort  than  a  steam  engine,  because 
the  electric  motor  exerts  a  constant  torque  upon  the  driving  wheels, 
whilst  the  steam  engine  does  not.  In  the  case  of  steam  locomotives, 
the  ratio  of  the  maximum  tractive  effort  to  the  weight  on  the  driving 
wheels  is  not  much  above  16  per  cent,  whereas  experience  has  shown 
that  with  electric  traction  this  is  increased  to  from  25  per  cent  to 
30  per  cent. 

The  cost  of  operating  electric  trains  will  also  be  reduced  by  the 
fact  that  only  one  man  is  required,  that  is  to  say,  only  a  driver  in- 
stead of  both  a  driver  and  a  fireman.  The  Board  of  Trade  should 
take  no  exception  to  this,  as  should  the  driver  be  incapacitated  in 
any  way,  the  method  of  control  employed  is  such  that  it  automatic- 
ally brings  the  train  to  a  standstill.  The  men  for  operating  these 
trains  need  not  be  mechanics,  and  the  work  will  be  cleaner  and  nicer, 
and,  therefore,  sought  after,  as  in  the  case  of  electric  trains,  the 
driving  cabin  is  entirely  inclosed  and  perfectly  clean. 

Electric  traction  is  much  more  flexible  than  steam,  and  trains 
can  either  be  split  up  into  units  of  one  or  two  cars  or  joined  up  into 
trains,  the  length  of  which  is  only  limited  by  the  length  of  plat- 
form available. 

There  are  other  advantages,  but  the  crowning  one  is  certainly  the 
much  higher  average  speed  due  to  rapid  acceleration  and  the  econ- 
omy of  power  and  labor,  as  well  as  the  reduced  cost  of  production 
which  is  everywhere  effected. 

An  incidental  advantage  in  favor  of  the  electric  motor  as  com- 
pared to  the  steam  engine  is  that  the  former  can  stand  an  amount 


DAWSON:     ELECTRIC  TRACTION  OH  BRITISH  RAILWAYS.    G7 

of  continuous  service  and  hard  usage  which  would  be  impossible 
with  the  latter,  besides  having  far  less  internal  friction. 

A  most  important  benefit  resulting  from  the  use  of  electric  trac- 
tion is  the  diminution  of  the  present  difficulties  due  to  the  lack  of 
accommodation  in  termini.  Mr.  Aspinall,  the  general  manager  of 
the  Lancashire  &  Yorkshire  railway,  stated  to  me  that  the  recent 
electrification  of  the  line  from  Liverpool  to  Southport  will  not  only 
double  the  carrying  capacity  of  the  line  but  will  also  practically 
double  the  terminal  accommodation. 

How  this  is  brought  about  is  easily  seen  when  we  consider  the  time 
wasted  at  present  in  getting  a  steam  train  out  of  a  station  after  it 
has  once  entered.  First  the  line  has  to  be  cleared  to  allow  another 
locomotive  to  back  on  to  the  train  in  readiness  to  take  it  out,  which 
it  does.  Then  before  another  train  can  be  brought  in  the  line  has 
to  be  cleared  again  so  that  the  original  locomotive  which  brought  in 
the  first  train  can  run  out.  These  various  manceuvers  occupy  a 
considerable  amount  of  time,  besides  necessitating  a  considerable 
amount  of  siding  accommodation,  not  to  mention  possible  blocking 
of  other  lines  by  the  steam  locomotives  constantly  either  running 
out  or  else  backing  on  to  the  trains. 

CONCLUSIONS. 

Comparatively  little  has  so  far  been  done  toward  the  introduction 
of  electric  traction  on  main  line  railways  in  Great  Britain.  This  is 
not"  surprising,  and  as  far  as  that  is  concerned,  neither  in  the  States 
nor  on  the  Continent  of  Europe  are  main  line  railways  at  present 
operating  anything  like  very  long  stretches  of  line  by  means  of 
electric  traction.  The  country  which  has  the  longest  stretches  of 
line  is  undoubtedly  Italy,  with  its  three-phase  3000-volt  line  work- 
ing with  overhead  trolley  between  Lecco  and  Sondrio,  and  its  third- 
rail  system  between  Milan,  Gallarate,  and  Varese,  both  of  which 
lines  have  been  exhaustively  described  in  the  technical  press  of  the 
world.  As  regards  this  country,  the  Lancashire  &  Yorkshire 
railway  has  equipped  and  is  operating  23  miles  of  route,  and  the 
North  Eastern  is  operating  40  miles  of  route,  both  on  the  third-rail 
system.  These  lines  have  only  recently  been  put  into  regular 
service,  and  no  figures,  either  as  regards  increase  of  traffic  or  cost 
of  operation,  are  as  yet  available;  the  only  results  so  far  obtained 
go  to  show  the  excessive  danger  of  third  rail.  In  this  country  a 
large  number  of  accidents  to  third  parties  have  taken  place,  some  of 


OS  DAWSON:     ELECTRIC  TRACTION  ON  BRITISH  RAILWAYS. 

them  fatal,  and  in  one  instance  a  train  has  been  set  on  fire  and 
seriously  damaged,  fortunately  with  no  loss  of  life.  These  results, 
as  far  as  they  go,  amply  confirm  the  conclusions  at  which  I  have 
arrived  and  are  strong  evidence  that  the  adoption  of  third  rails,  at 
any  rate  on  main  line  railways,  is  not  at  all  desirable. 

There  are  several  lines  in  this  country  operating  at  high  speeds 
with  fairly  heavy  loads  and  many  others  are  being  constructed. 
There  is,  for  instance,  the  Mersey  railway,  the  City  &  South  Lon- 
don, the  Central  London,  the  Great  Northern  &  City,  and  the 
Liverpool  Overhead,  all  of  which  have  been  working  most  satis- 
factorily for  a  considerable  number  of  years,  as  well  as  the  Metro- 
politan, the  Metropolitan  District,  and  other  tube  lines  now  being 
constructed  by  the  Underground  Electric  Eailway  Company  of  Lon- 
don and  which  will  commence  working  next  year.  The  power  sta- 
tion which  will  supply  energy  for  the  last-mentioned  railways  is.  so 
far,  the  largest  that  has  ever  been  built. 

To  give  some  idea  of  the  large  amount  of  railways  which  already 
exist  in  London,  the  following  tabulated  statement  may  not  be  with- 
out interest.  I  have  taken  them  from  figures  published  by  that 
eminent  American,  the  Hon.  Eobert  P.  Porter: 

RAILWAYS  RUNNING  INTO  LONDON. 
North  Side. 


t 

Railway.                                                Un 

-  >  i 

Great  Central  

e"#th  of     Number  of 
es  within      stations 
county.           wiU  in 
[miles).         county. 

2.37               1 
16.79             27 
4.31               4 

4.75               4 
9.64             12 
.62               1 
12.25             18 
10.42             16 
2.12               8 
7.27               6 
1.92               6 

Great  Eastern  

Great  Northern  

Great  Western  '  

London  &  North  Western     

London  Tilbury  &  Southend  

Metropolitan  

Metropolitan  District  

Metropolitan  &  Metropolitan  District  (joint)  .  .  . 
Midland    

Totten  &  Hampstead  Junction  

Total  . 

72.46 

103 

DAWSON:    ELECTRIC  TRACTION  ON  BRITISH  RAILWAYS.    09 
South  Side. 

Tergthof     Number  of 

T?«5!r«rax/  UD68  Within        Stations 

••"••*  county  within 

(miles).  county. 

London,  Brighton  &  South  Coast 31 . 14  29 

London,  Chatham  &  Dover 26 . 22  33 

London  &  South  Western 14.05  12 

South  Eastern 37.86  27 

London  &  South  Western  and  London  &  South 

Coast  (joined) .60 

Totals 109.87  101 

Wholly  in  London. 

City  of  London  Electric 6 . 50  13 

City  &  South  London  Electric 6.65  14 

East  London  7.22  7 

Hammersmith  &  City 3 . 00  5 

North  London 11.19  18 

Waterloo  &  City  Electric 1.50  2 

West  London 2 . 30  2 

West  London  Extensions 4. 76  4 

Whitechapel  &  Bow 3.00  4 

Totals   46.12  69 

Making  a  grand  total  of 228.45  273 


In  this  connection  it  must  be  borne  in  mind  that  the  mileage 
here  given  are  miles  of  route  and  not  miles  of  single  track,  and  that 
they  only  represent  the  miles  of  route  actually  inside  the  county  of 
London.  In  order  to  represent  the  actual  mileage  which  is  only,  or 
to  a  large  extent,  devoted  to  suburban  service,  the  total  would  have 
to  be  more  than  doubled;  in  the  case  of  the  London,  Brighton  & 
South  Coast  railway  only  just  over  31  miles  of  route  are  given, 
whereas  the  suburban  system  comprises  75  miles,  and  on  this  sys- 
tem, the  average  distance  between  stations  does  not  exceed  one  mile. 
A  glance  at  a  railway  map  of  London  and  its  environs  clearly  shows 
the  enormous  network  of  railways  which  converge  into  the  center 
of  the  city,  and  a  careful  examination  of  such  a  map  on  which  the 
existing  electric  tramways  and  light  railways  have  been  drawn  will 


70  D4WSON:     ELECTRIC  TRACTION  ON  BRITISH  RAILWAYS. 

show  how,  in  the  next  few  years,  the  electric  tramways  and  light 
railways  will  enable  passengers  to  travel  from  any  portion  of  Lon- 
don to  places  from  20  to  30  miles  outside  the  center  of  the  city. 
Under  the  existing  conditions  it  would  in  many  cases  be  advan- 
tageous for  passengers  to  travel  as  far  as  15  miles  by  tramway  in- 
stead of  taking  the  steam  railway,  owing  both  to  the  low  average 
speed  and,  in  many  cases,  the  long  interval  between  the  trains. 

What  has  been  stated  as  regards  London,  applies  quite  as  well  to 
other  large  towns  of  the  United  Kingdom,  and  I  am  firmly  con- 
vinced that  there  is  no  country  in  which  electrification  will  be  a 
greater  benefit  to  the  railways  than  the  United  Kingdom.  I  believe 
that  the  British  railway  companies  are  rapidly  realizing  that  a  move 
will  become  necessary,  and  when  once  the  movement  begins,  the 
transformation  as  regards  our  railways  will  be  quite  as  great  as 
that  which  has  taken  place  during  the  last  few  years  with  tramway 
construction. 

DISCUSSION. 

CHAIRMAN  DUNCAN:  The  paper  abstracted  by  Mr.  Armstrong  is  now 
open  for  discussion. 

Mr.  H.  WARD  LEONARD:  There  is  one  figure  that  drew  my  attention 
in  the  eaily  part  of  the  paper,  and  that  is  the  statement  of  the  very  high 
capitalization  of  the  English  roads,  as  an  average.  I  can  only  speak  from 
memory,  but  I  believe  that  the  most  efficient  railway  as  regards  earnings 
we  have  —  the  Pennsylvania  railroad  —  has  a  capitalization  of  about 
$370,000  per  mile, —  which  is  about  50  per  cent  in  excess  of  the  figure 
named.  So  that  very  high  capitalization,  while  of  course  it  is  of 
tremendous  importance,  is  not  necessarily  an  indication  of  poor  earning 
capacity.  The  average  figure  in  New  York,  Pennsylvania,  and  New  Jersey 
which  is  the  part  of  the  United  States  most  fairly  comparable  with 
England  is  about  $120,000  a  mile. 

Mr.  F.  J.  SPBAGUE:  You  refer  now  to  single  or  double  tracks?  And 
does  the  paper  refer  to  single  or  double  tracks? 

SECRETARY  ARMSTRONG:  It  is  per  mile  of  road.  It  is  partly  single 
and  partly  double. 

Mr.  LEONABD:  The  figures  I  have  named  are  all  per  mile  of  road.  The 
figures  I  have  stated  are  from  the  statistics  of  the  United  States  Railway 
Commission  Reports.  They  are  per  mile  of  road,  that  is,  per  mile  of  line. 

I  think  it  is  quite  proper  to  emphasize  the  statement  the  author  has 
made  in  the  paper  as  to  the  steam  locomotive  having  to  carry  around 
with  it  continuously  a  very  large  number  of  tons  that  are  entirely  idle. 
I  think  it  would  probably  be  conservative  to  say  that  the  net  cost  repre- 
sented by  the  ton  miles  of  a  locomotive  due  to  the  non-tractive  part  of  a 
heavy  freight  locomotive  in  this  country  would  be  not  far  from  $50  p*.r 
day.  And  that  brings  up  another  point,  namely,  that  in  discussions  on 
this  subject,  a  great  deal  of  attention  is  usually  spent  on  the  cost  of 


DAW  SON:     ELECTRIC  TRACTION  ON  BRITISH  RAILWAYS.    71 

fuel,  and  the  question  of  whether  or  not  it  would  be  possible  to  save  the 
wages  of  the  fireman.  Personally,  I  consider  all  those  matters  as  ex- 
tremely trivial  as  compared  with  the  really  important  matters.  Con- 
sidering $100  of  earnings  by  railways  of  this  country  only  about  $7  of 
that  amount  is  spent  for  fuel.  So  that  it  does  not  seem  advisable  to 
confine  the  discussion  so  much  to  fuel  consumption. 

I  think  that  the  very  greatest  importance  should  be  laid  upon  the  re- 
quirement of  endeavoring  to  utilize  to  the  highest  degree  the  very  large 
investments  and  fixed  charges  that  are  represented  by  the  equipment  and 
maintenance  of  a  mile  of  road.  Something  like  86  per  cent  of  the  total 
cost  of  moving  a  ton-mile  is  represented  in  this  way,  and  is  totally 
independent  of  the  coal  and  wages  on  the  train.  And  it  seems  to  me  con- 
spicuous that  the  problem  narrows  itself  down  to  the  question  of  getting 
from  every  mile  of  track  per  hour  the  maximum  possible  ton  miles  — 
which  means  again  the  maximum  possible  number  of  tons  moved  at  the 
highest  possible  rate  of  speed. 

If  we  go  back,  for  example,  in  the  statistics  of  the  Pennsylvania  Rail- 
way for  about  thirty  years  we  find  that  the  cost  of  moving  a  ton  one 
mile  used  to  be  at  that  time  about  a  cent  and  six-tenths;  and  in  1902 
the  cost  of  moving  a  ton  one  mile  by  the  same  railway  was  thirty-six 
hundredths  of  one  cent.  Now,  this  very  striking  reduction  in  the  cost  of 
moving  freight  has  not  been  in  any  way  due  to  any  reduction  in  cost  of 
wages  or  cost  of  coal.  On  the  contrary,  those  have  increased.  And  per- 
sonally I  am  strongly  of  the  belief  that  to-day  the  cost  of  moving  freight 
is  inversely  proportionate  to  the  power  that  is  employed  in  moving  the 
train,  and  with  that  thought  in  mind  it  seems  to  me  that  the  electric 
moving  of  freight  has  possibilities  that  are  not  at  all  to  be  expected  from 
any  steam  operation. 

There  are  probably  not  more  than  10  per  cent  of  the  locomotives  that 
are  used  in  this  country  that  are  capable  of  developing  over  1000  horse- 
power. Those  large  locomotives  are  the  most  economical  ones  we  have 
as  regards  moving  freight.  There  are  some  40,000  locomotives  in  the 
United  States,  and  less  than  4000  of  them  are  of  modern  efficient  size.  The 
boiler  is  the  principal  limitation  to  the  power  of  the  locomotive,  and  it 
seems  unlikely  that  there  will  be  very  much  growth  in  the  power  of  the 
boiler  used  on  steam  locomotives;  whereas,  theoretically  speaking,  there 
is  no  limit  to  the  amount  of  power  that  could  be  applied  to  the  move- 
ment of  a  freight  train  by  electricity. 

The  draw-bar  pull  of  the  freight  locomotive,  in  the  best  types,  reaches 
sometimes  as  high  as  50,000  pounds,  but  that  draw-bar  pull  is  only 
obtained  when  steam  is  taken  at  full  stroke, —  which  means  at  an  ex- 
tremely slow  rate  of  speed,  and  by  the  time  such  a  rate  of  speed  is 
reached  as  would  represent  the  average  speed  desired  the  draw-bar  pull 
is  less  than  half  of  that  figure. 

The  mountain  sections  of  our  principal  railways  are  the  places  where 
the  requirements  for  power  are  most  keenly  felt  to-day.  There  is  always 
a  great  congestion  of  freight  at  such  places.  If  we  employ  electric  loco- 
motives we  have,  fortunately,  coincident  with  the  grades  of  those  nioun- 


72  DAWSON:     ELECTRIC  TRACTION  ON  BRITISH  RAILWAYS. 

tain  sections,  as  a  usual  thing,  power  in  cheap  form  repre?ented  by  the 
water  power  of  the  mountain  section. 

It  seems  to  me  that  what  is  wanted  is  a  locomotive  which  will  produce 
about  50,000  pounds  draw-bar  pull  and  maintain  that  at  about  thirty 
miles  per  hour  —  and  that  means  4000  horse-power  at  the  draw-bar.  We 
already  are  subjecting  our  draw-bars  to  that  strain,  and  they  are  strong 
enough  to  stand  it,  provided  that  we  have  some  form  of  operation  which 
is  not  going  to  subject  those  draw-bars  to  intermittent  large  strains  due 
to  irregular  methods  of  control,  or  to  the  bucking  of  the  various  units 
that  are  employed  under  multiple  control. 

It  seems  to  me  that  the  principal  cause  of  the  poor  showing  of  the  British 
railroads  in  the  cost  of  handling  freight,  as  compared  with  the  United 
States,  can  be  found  in  the  fact  that  as  an  average  the  horse-power  of 
their  locomotive  is  very  small  compared  with  the  best  practice  in  this 
country. 

Mr.  SPRAGUE:  I  have  only  a  few  words,  Mr.  Chairman,  on  this  paper. 
Not  having  read  it,  I  am  not  prepared  to  discuss  it  at  length.  Probably 
in  what  little  I  say  I  may  disagree  with  Mr.  Dawson,  and  to  some  extent 
with  what  Mr.  Leonard  has  said.  In  one  form  or  another  I  have  for  many 
years  advocated  electric  traction.  It  has  already  naturally  supplanted  a 
method  of  traction  which  at  the  best  was  poor  —  that  is,  animal  traction ; 
and  in  supplanting  it,  it  has  achieved  results  in  transportation  greater 
than  its  most  ardent  advocates  had  hoped,  in  cheapening  operating  cost, 
increasing  schedule  speeds  and  opening  up  new  fields. 

But  we  must  not  forget  that  one  of  the  chief  reasons  for  the  great 
success  of  the  electric  railway  has  been  the  fact  that  it  has  been  what  may 
be  called  a  house-to-house  railway,  one  making  frequent  stops  convenient 
to  the  passenger.  As  a  result  we  have  seen  here  in  the  United  States 
practically  every  horse-car  disappear,  almost  all  cables  abandoned,  exist- 
ing lines  consolidated,  and  new  lines  link  together  towns  and  cities  and 
wipe  out  the  divisions  between  urban  and  rural  communities. 

But  when  approaching  the  steam  railway  problem  I  have  always  done 
so  with  a  good  deal  of  deference  to  existing  conditions.  Electricity,  after 
all,  is  merely  a  convenient  method  of  transmitting  power.  We  do  not 
create  anything  by  it,  we  do  not  establish  any  new  laws  by  its  use.  By 
concentrating  at  central  stations  the  power  used  on  a  railroad  and  dis- 
tributing it  in  the  best  possible  manner  we  hope  to  utilize  that  power  more 
economically.  But  in  order  to  do  so  successfully  from  a  power  standpoint 
there  is  one  essential;  the  load  factor  must  be  high,  which  brings  me  back 
to  an  assertion  which  I  have  made  again  and  again  for  the  last  fifteen 
years;  namely,  that  leaving  out  for  the  moment  the  influence  of  competing 
lines,  diversion  of  traffic  and  what  not,  there  H  a  point  on  any  railroad 
where  the  adoption  of  electricity  may  be  justified,  and  that  point  is 
primarily  determined  by  one  essential,  density  of  traffic.  And  I  do  not 
mean  by  density  of  traffic  concentration  of  loads  at  one  point,  but  multi- 
plicity of  units  well  distributed.  So  long  as  the  operation  of  any  road 
means  the  sending  out  of  high  powered  units  at  long  and  irregular  in- 
tervals over  great  distances  we  might  as  well  be  frank  with  ourselves  and 
say  that  there  is  not  the  field  for  electric  transportation. 


DAW  SON:     ELECTRIC  TRACTION  ON  BRITISH  RAILWAYS.    73 

As  the  traffic  increases  we  approach  a  point  where  the  number  of  units 
between  terminal  points  warrants  the  consideration  of  a  change  of  motive 
power,  and  I  think  that  condition  has  arisen  on  a  number  of  steam  rail- 
roads. Beyond  that  point  there  can,  I  think,  be  very  little  question  as  to 
whether  electricity  can  be  economically  adopted. 

The  problems  in  Great  Britain,  the  Continent  and  the  United  States  are 
somewhat  different.  Here  it  will  be  many  years  before  we  can  in  even 
the  most  hopeful  attitude  look  for  many  of  our  main  roads  to  be  operated 
other  than  by  steam.  There  are  some  roads  and  certain  sections  of  rail- 
roads which  will  undoubtedly  be  operated  by  electricity  —  but  oftentimes 
for  reasons  not  determined  by  economy  of  operation. 

I  may,  perhaps,  cite  the  most  important  two  instances  in  this  country, 
if  not  in  the  world,  at  present  —  the  operation  of  the  Pennsylvania  Rail- 
road tunnels  and  terminals  in  Jersey  City,  New  York  and  Long  Island, 
and  then  those  of  the  New  York  Central  Railroad  in  New  York  and  a  part 
of  its  main  line.  I  have  the  honor  to  be  a  member  of  the  Commission  on 
the  latter  road,  which  has  to  do  with  the  electrification  of  the  equipment. 
It  is,  perhaps,  too  soon  to  go  into  details  in  connection  with  it,  except 
this :  One  of  the  requirements  —  a  legal  one  —  which  determined  the  use 
of  electricity  on  this  road  was  that  no  steam-operated  train  should  be 
used  below  the  Harlem  River.  The  Harlem  River  is  well  within  the  city 
limits  of  New  York,  and  only  a  comparatively  short  distance  from  the 
terminal  at  42nd  Street.  The  movement  of  trains  within  that  district  is 
enormously  congested.  According  to  a  report  made  by  Mr.  Arnold  some- 
time ago,  at  certain  periods  there  are  over  700  daily  train  movements,  and 
the  trains  vary  anywhere  from  150  to  700  tons  in  weight. 

The  law  said  we  should  abandon  the  use  of  steam.  Of  course,  we  were 
permitted  to  use  anything  else  in  the  tunnel,  but  that  was  practically  the 
same  as  saying  that  electricity  should  be  used.  But  within  even  the 
district  determined  for  electrical  operation  extending  out  some  35  miles, 
I  do  not  think  any  calculation  made,  taking  into  account  the  interest  on 
investment,  shows  any  real  economy  in  operation  over  steam,  all  things 
considered. 

The  determining  considerations  may  be  stated  as  first,  the  law  which 
practically  required  the  use,  part  of  the  way,  which  part  was  to  a  point 
where  there  were  no  terminal  facilities  whatever,  and  second,  that  it  was 
advisable  from  a  transportation  standpoint  to  operate  suburban  trains 
electrically  —  certainly  within  a  distance  of  perhaps  an  hour's  run  to 
New  York.  Having  determined  that,  then  it  was  common  sense  to 
operate  all  trains  located  within  that  zone  by  electricity,  instead  of  having 
a  duplicate  system. 

The  result  is  that  for  some  distance  from  New  York  city  we  will  have 
what  may  be  considered  a  great  terminal,  within  which  there  are  suburban 
trains  operated  by  motors  under  the  cars  on  the  multiple-unit  plan,  and 
other  trains  dropping  off  their  steam  locomotives  at  the  termini,  and 
taking  on  electric  locomotives  likewise  so  operated. 

It  is,  perhaps,  unwise -to  attempt  any  limitation  as  to  this  particular 
development.  Certainly  I  would  not  be  rash  enough  to  hazard  it,  but  it  is 
a  special  problem,  and  I  do  not  think  has  yet  any  great  bearing  upon  the 


74  DAWSON:     ELECTRIC  TRACTION  ON  BRITISH  RAILWAYS. 

broad  question  whether  trunk  railways  will  be  operated  by  electricity. 
There  are  many  other  problems  to  be  taken  up  when  that  subject  is  con- 
sidered. 

The  British  railways,  especially  those  terminating  in  London,  will 
mostly  adopt  electricity  only  when  they  are  compelled  to;  few  of  them 
will  do  it  of  their  own  volition.  The  competition  which  exists  in  this 
country  with  electric  railways  will  not  be  quite  so  forcibly  felt  on  English 
roads,  because  there  is  not  that  same  freedom  in  granting  of  franchises 
tor  parallel  lines  of  railways  that  we  have  here.  But  there  is  a  special 
reason  why  electric  equipment  should  be  considered.  The  traffic  in  Lon- 
don, for  example,  is  enormously  congested  at  certain  times  of  the  day. 
The  result  is  that  the  facilities  are  entirely  inadequate,  and  new  con- 
struction, whether  of  an  overhead  line  over  existing  tracks,  or  tunnels 
beneath  or  tracks  parallel  to  them,  is  almost  prohibitive  in  cost.  So  that 
the  natural,  and  so  far  as  I  can  see  about  the  only  way,  in  which  they 
can  increase  their  capacity  is  by  electric  equipment,  and  I  think  that  the 
British  roads  in  time  will  see  that  fact. 

Perhaps  one  of  the  most  important  means  by  which  the  changes  could 
be  brought  about  would  be  in  the  reduction  of  the  age  limit  in  their 
directorates.  You  gentlemen  know  the  English  and  American  practice  is 
somewhat  different  in  this  regard.  When  a  man  becomes  a  director  on  an 
English  railway  the  position  practically  terminates  only  at  his  death  or 
permanent  disability,  or  when  for  some  good  practical  reason  he  gives 
away  to  another.  He  rarely  represents,  in  that  conservative  method 
which  governs  English  railways,  the  progressive  element  of  the  stock- 
holders. Being  a  man  of  mature  years,  and  often  having  reached  that  age 
when  most  men  are  ultra  conservative,  he  will  hesitate  to  abandon  an 
existing  system  and  adopt  another.  It  usually  takes  younger  men  to  do 
that,  and  to  believe  what  can  be  accomplished  by  such  a  change. 

Here  in  the  United  States  the  directors  have  not  that  hold  upon  the 
administration  that  they  have  abroad.  A  change  of  ownership  in  the  road, 
a  change  in  the  holdings  of  the  stock,  may  result  in  a  very  prompt  and 
radical  change  in  its  management  from  the  president  down,  but  such  a 
thing  is  almost  impossible  in  the  British  Isles. 

I  do  not  know  that  there  is  anything  further,  Mr.  Chairman,  that  I 
want  to  add.  In  fact,  I  did  not  intend  to  say  anything.  I  am  as  hopeful, 
perhaps,  as  any  one  can  be  that  electricity  will  be  used  on  steam  railroads, 
but  I  do  not  want  to  shut  my  eyes  to  the  fact  that  there  are  a  good 
many  difficulties  inherent  to  trunk-line  railway  service  for  which  elec- 
tricity is  no  cure-all. 

Mr.  LEONARD:  Mr.  Chairman,  if  I  may  be  allowed  to  add  a  word,  I 
should  like  to  speak  of  one  point  I  have  heard  frequently  raised  and  it 
seems  a  fitting  opportunity  to  mention  it.  In  comparing  the  cost  of 
operation  of  English  railways  with  American  railways,  I  find  that  the 
Englishmen  are  very  apt  to  retreat  behind  the  argument  that  in  England 
the  mail  and  express  business  is  classified  in  the  freight  figures,  whereas 
we  in  this  country  have  those  classified  in  the  passenger  business,  and 
receive  compensation  for  those,  which  make  so  important  a  factor  as  to 
distort  the  figures  materially;  and  that,  therefore,  deductions  cannot  be 


DAWSON:     ELECTRIC  TRACTION  ON  BRITISH  RAILWAYS.    75 

fairly  drawn  by  comparison  in  the  cost  per  ton-mile  of  the  English  rail- 
\vays  and  the  American  railways. 

The  express  is  2  per  cent  of  the  receipts  in  this  country,  and  the  mail 
also  about  2  per  cent  of  the  total  receipts,  so  that  those  figures  are  not 
sufficiently  influential  to  in  any  way  influence  the  very  striking  difference 
in  the  costs.  About  nine-tenths  of  our  present  steam  locomotives  in  our 
country  seem  to  me  a  liability,  rather  than  an  asset,  to  the  railways  that 
operate  them;  and  since  there  seems  to  me  to  be  a  necessity  for  "scrap- 
ping" about  nine-tenths  of  the  inefficient  small  locomotives  and  the  re- 
placement of  them  by  the  larger  efficient  ones,  we  are  not  confronted  with 
the  same  condition  of  affairs  as  we  would  be  if  the  steam  railways  had 
already  made  a  comprehensive  equipment  of  the  highest  class  of  steam 
locomotives. 


THE   MONORAIL  RAILWAY. 


BY  F.  B.  BEHR. 


For  many  years  eminent  engineers,  including  the  great  Telford 

in  1828,  have  taken  great  interest  in  designing  single-rail  rail- 
ways, and  many  patents,  covering  a  variety  of  forms  and  combina- 
tions, have  been  taken  out,  but  none  of  these  attempts  have  been 
carried  to  a  practical  issue  until  recently.  Within  a  comparatively 
recent  period,  however,  two  systems  have  been  so  far  perfected 
as  to  offer  real  practical  value  as  means  of  transportation  for 
passengers  and  goods. 

Of  these  two  systems,  one  is  identified  with  the  author,  and 
the  other  is  known  under  the  name  of  the  Langen  system,  and 
is  used  to  connect  the  towns  of  Barmen  and  Elberfelde,  Germany. 
This  paper  will  more  especially  describe  the  development  and  ap- 
plication of  the  former  system.  No  claim  is  made  by  the  author 
of  this  paper  as  the  originator  of  the  fundamental  principle  of 
the  system  of  monorail  railway.  It  is  difficult  to  trace  who  first 
suggested  it,  as  there  were  several  almost  simultaneous  attempts 
in  that  direction  between  the  years  of  1875  and  1884.  His  only 
claim  is  to  having  taken  up  the  original  idea  in  1884,  when  it  was 
still  in  its  simplest  and  most  primitive  shape;  to  having  developed 
the  general  ideas  and  principles  of  others  in  designing  the  prac- 
tical details;  and  to  having  constructed  for  the  first  time,  in  1886 
for  steam  power  and  in  1896  for  electricity,  monorails  which  have 
been  worked  successfully  for  the  carrying  of  passengers  and  goods. 

The  Behr  monorail  is  applicable  to  three  distinct  purposes, 
namely,  to  light  railways  in  sparsely  populated  districts  and  in 
hilly  countries  where  they  would  serve  as  feeders  to  existing  rail- 
ways, as  elevated  railways  in  towns,  and  as  supplementary  to  ex- 
isting systems  of  mail  lines  all  over  the  world  for  carrying  express 
passenger  traffic,  mails  and  parcels  at  much  higher  speeds  and  with 
much  greater  frequency  of  trains. 

The  advantages  over  ordinary  lines  in  the  first  of  these  appli- 
cations, result  principally  from  the  possibility  of  using  very  sharp 

[76] 


BEER:     MONORAIL  RAILWAY.  77 

curves,  avoiding  the  expense  of  earthworks  and  tunnels,  and  also 
from  the  smaller  cost  of  bridges,  etc.  The  result  of  this  economy 
would  be  about  50  per  cent  in  hilly  countries,  in  comparison  with 
an  ordinary  meter  gauge  railway. 

The  special  principle  of  the  Behr  monorail  was  in  1883  applied 
by  Mr.  Charles  Lartigue  in  the  construction  of  some  primitive 


FIG.  1.    PROPOSED  METROPOLITAN  RAILWAY  FOB  CHELSEA  EMBANKMENT, 

LONDON. 


lines  in  Algeria  and  Tunis  for  carrying  esparto  grass  and  similar 
produce,  the  tractive  power  being  by  animals  in  all  cases. 

An  experimental  line  was  built  by  the  author  in  London,  in  the 
rear  of  Victoria  street,  Westminster,  in  the  year  1886,  where  for 
the  first  time  locomotives  and  carriages  were  run  on  a  monorail. 
On  the  section  was  a  gradient  of  1  in  10,  and  for  about  a  year 
the  engine  took  up  this  incline,  without  a  rack,  one  light  carriage 
besides  its  own  weight,  showing  that  the  adhesion  on  this  form 
of  railway  is  considerably  greater  than  on  an  ordinary  two-rail 


78 


BEER:     MONORAIL  RAILWAY. 


railway,  on  which  on  such  an  incline  an  engine  is  hardly  able  to 
pull  up  its  own  weight. 

An  act  of  Parliament  for  a  railway  from  Listowel  to  Bally- 
bunion,  in  Ireland,  for  regular  passenger  and  goods  traffic,  was 
obtained  in  July,  1887,  and  the  line  was  passed  by  the  Board 
of  Trade  and  opened  to  the  public  March  1,  1888.  It  has  been 
working  ever  since  without  any  difficulty  or  accidents,  and  in  over 
16  years  has  not  been  subject  to  a  single  claim  for  compensation 
of  any  kind.  The  line  is  especially  remarkable  for  its  very  sharp 
curves,  the  smallest  having  a  radius  of  54  feet. 

The  second  application,  as  an  elevated  railway  in  towns,  is  of 
very  great  importance,  especially  in  the  United  States,  where  such 


FIG.  2. 


CAB  FOB  PROPOSED  MANCHESTER  AND  LIVERPOOL  ELECTRIC 
EXPRESS  RAILWAY. 


railways  are  in  common  use.  Elevated  railways  of  this  system 
in  towns  could  be  built  at  a  very  much  smaller  cost,  with  much 
less  obstruction  of  the  ordinary  road  traffic,  requiring  much  less 
room  on  the  roads,  with  much  less  obstruction  of  both  light  and 
air. 

Such  a  line  has  been  proposed  for  the  Chelsea  Embankment,  in 
London,  to  Putney  Bridge.  The  cost  of  the  line  (double  track) 
would  be  under  $200,000  per  mile.  The  system  has  also  been  pro- 
posed for  another  metropolitan  line  in  London,  about  17  miles 
long,  starting  in  the  west  end  and  going  to  the  city  and  docks, 
and  nowhere  along  any  street,  merely  crossing  streets.  The  total 
cost  of  this  line,  double  track,  is  estimated  at  about  $500,000  per 
mile. 

Passing  next  to  the  question  of  high  speeds,  the  great  merit 
of  this  system  for  high-speed  service  is  that  the  cars  are  absolutely 
underailable;  that  it  possesses  important  economic  advantages  for 


BEER:     MONORAIL  RAILWAY.  79 

working  at  very  high  speeds;  and  that  the  rise  in  grade  in  ap- 
proaching stations  greatly  helps  the  acceleration  of  the  trains  when 
starting  and  is  of  equally  great  assistance  in  stopping  the  trains 
when  approaching  a  station.  The  cost  of  construction  of  such 
lines  is  generally  slightly  less  for  a  speed  of  100  to  110  miles  an 
hour  than  the  cost  of  an  ordinary  two-rail  railway  for  speeds  of 
50  to  60  miles  an  hour. 

There  are  many  causes  which  contribute  to  the  absolute  safety 
of  the  system  which  can  only  be  understood  by  carefully  examin- 
ing the  detailed  construction  of  the  carriage  as  it  fits  to  the  track, 
when  it  will  be  observed,  among  other  things,  that  whereas  an 
ordinary  railway  carriage  is  held  on  the  rails  by  a  flange  of  about 
three-fourths  of  an  inch  in  depth,  the  arrangement  of  the  mono- 
rail carriage  is  really  equivalent  to  a  continuous  flange  of  over 
three  feet  in  depth.  A  feature  of  great  importance  to  the  pas- 
senger is  that  it  is  not  only  a  safe  way  of  traveling,  but  it  looks 
also  very  safe  and  produces  on  the  mind  of  the  traveler  a  feeling 
of  absolute  security. 

On  an  experimental  elevated  high-speed  monorail  built  in  1897, 
with  a  carriage  weighing  about  72  tons,  a  speed  of  84  miles  per 
hour  was  obtained  over  curves  of  1500  ft.  radius,  and  a  speed 
of  70  miles  per  hour  on  an  ascent  of  1  in  90.  It  was  a  much 
greater  feat  to  attain  84  miles  an  Hour  on  such  a  line  and  on  such 
curves,  with  straight  sections  so  short  that  it  was  impossible  to 
construct  a  proper  parabola  between  them  and  the  curve,  than 
to  attain  a  speed  of  110  miles  on  a  properly  constructed  monorail, 
under  such  conditions  as  would  arise  in  ordinary  railway  practice. 

This  line  consisted  only  of  embankments  about  25  ft.  high 
and  cuttings  20  ft.  deep,  with  a  total  fall  of  130  ft  in  1% 
miles.  The  road  was  built  during  a  very  wet  winter  in  a  few 
months,  and  worked  immediately  afterwards  during  a  very  wet 
summer,  when  considerable  portions  of  the  embankments  had  prac- 
tically been  washed  away,  and  many  of  the  sleepers  were  really 
suspended  in  mid-air.  Notwithstanding  these  conditions,  experi- 
ments were  carried  out  during  a  period  of  over  twelve  month? 
without  a  single  accident.  The  line  was  three  miles  in  length, 
and  formed  by  two  short  straight  lines  joined  by  two  curves  at 
each  end,  so  that  continuous  runs  of  any  length  could  be  made. 
But  as  there  was  a  fall  of  130  ft.,  it  was  necessary  to  rise  to  the 
same  level,  so  that  to  develop  the  speed  there  was  practically  only 
a  length  of  about  one  and  one-half  miles,  and  the  highest  speed 


80  BEER:     MONORAIL  RAILWAY. 

of  84  miles  an  hour  always  occurred  at  the  bottom  of  the  incline, 
at  the  center  of  a  curve  of  1500  ft.  radius. 

The  British  Parliament  has  authorized  and  the  Board  of  Trade 
has  approved  the  construction  of  a  monorail  between  Manchester 
and  Liverpool,  on  condition  that  the  speed  shall  not  exceed  110 
miles  an  hour.  The  sharpest  curve  to  which  this  speed  applies 
has  a  radius  of  1800  ft.  The  whole  of  the  materials  proposed 
to  be  used  in  its  construction,  above  the  level  of  the  sleepers,  will 
be  of  steel.  The  maintenance  will  be  similar  to  that  on  an  ordi- 
nary railway,  as  there  will  be  practically  no  difference  in  the 
manner  of  packing  the  sleepers  or  of  inspecting  the  various  parts. 
For  the  greater  security,  however,  of  the  workmen  employed  on 
the  line,  the  clear  space  left  between  two  trains  passing  will 
be  3  ft.,  as  against  1  ft.  8  in.,  the  space  provided  between  Pullman 
cars. 

All  trains  will  consist  of  only  one  car,  for  reasons  of  safety, 
economy  in  working  and  construction,  and  for  the  convenience  of 
the  public.  There  are  three  classes  of  cars  designed  and  approved 
for  this  line.  The  smallest  car  will  carry  40  passengers,  the  second 
size  52  and  the  largest  80.  It  is  proposed  to  begin  the  service 
between  Manchester  and  Liverpool  with  cars  carrying  40  passengers 
each  and  running  every  10  minutes.  The  working  expenses  of 
this  service  at  110  miles  an  hour,  including  maintenance  repairs, 
management  and  everything  else,  are  estimated  at  less  than  15 
cents  per  train  mile. 

The  center  of  gravity  of  this  carriage  is  at  least  12  inches  below 
the  top  surface  of  the  monorail,  as  required  by  the  Act  of  Parlia- 
ment. The  whole  working  of  this  line,  which  will  carry,  if  neces- 
sary, 48,000  passengers  a  day  at  a  speed  of  110  miles  an  hour, 
doing  the  whole  distance  in  20  minutes,  is  very  simple.  Collisions 
are  impossible,  there  are  no  level  crossings,  no  switches,  and  not- 
withstanding the  number  of  passengers  carried,  there  are  never 
more  than  two  carriages  on  the  whole  line  from  end  to  end. 

With  regard  to  the  electrical  working,  full  details  cannot  be 
given,  as  the  author  does  not  consider  that  he  is  especially  quali- 
fied for  that  purpose.  The  joint  electrical  engineers  for  the  Man- 
chester and  Liverpool  Kailway  are  Lord  Kelvin  and  Sir  W.  H. 
Preece.  Following  are  given,  however,  some  general  data: 

The  distance  to  be  traversed  is  34%  miles,  without  a  stop,  in  20 
minutes.  The  acceleration  at  starting  is  to  be  2  ft.  per  second  per 


BEER:     MONORAIL  RAILWAY.  81 

second,  diminishing  to  9  in.  per  second  per  second  or  an  average 
of  iy2  ft.  per  second  per  second,  attaining  a  speed  of  110  miles 
in  1  minute  47  seconds  and  in  a  distance  of  under  2  miles.  The 
resistance  due  to  friction  and  air  pressure  is  taken  at  45  Ibs.  per 
ton  at  full  speed.  The  coefficient  of  adhesion  is  taken  at  about  one- 
sixth,  say  400  Ibs.  per  ton  for  the  worst  weather.  The  total  weight 
of  the  car  is  over  40  tons  and  the  weight  of  the  driving  wheels 
is  20  tons;  hence  the  limit  of  adhesion  that  can  be  calculated  on 
these  driving  wheels  under  all  circumstances  is  over  200  Ibs.  per 
ton  plus  15  Ibs.  per  ton  weight  for  air  resistance,  giving  a  total  of 
215  Ibs.  per  ton  weight,  being  more  than  the  weight  required,  as 
140  Ibs.  per  ton  is  all  that  is  necessary  for  an  acceleration  of  2  ft. 
per  second  per  second. 

For  braking  purposes,  a  high-speed  Westinghouse  brake  will  be 
able  to  retard  the  train  at  the  rate  of  3  ft.  per  second  per  second, 
which  will  absorb  210  Ibs.  per  ton  weight  of  the  car  distributed 
over  the  four  wheels,  or  52%  Ibs.  per  ton  per  wheel.  This  will 
stop  the  car  in  about  1380  yds.  If,  in  addition  to  this,  the  motors 
are  short-circuited,  the  remaining  adhesion  can  be  utilized  on  the 
two  driving  wheels,  which  amounts  to  another  52%  Ibs.  per  ton  per 
wheel,  and  is  sufficient  for  an  additional  retardation  of  1  ft.  6  in. 
per  second  per  second.  This  will  give  a  total  retardation  of  4  ft. 
6  in.  per  second  per  second,  and  would  stop  the  car  in  768  yds. 
In  this  arrangement,  the  retardation  produced  by  the  motors  will 
be  at  exactly  the  ratio  of  the  average  acceleration  to  attain  the 
full  speed.  If  the  shortrcircuiting  of  the  motors  was  used  alone 
without  the  Westinghouse  brake  for  stopping  the  train,  there  would 
be  an  available  adhesion  on  the  driving  wheels  of  215  Ibs.  per  ton 
weight  of  the  car,  amply  sufficient  for  a  retardation  of  3  ft.  per 
second  per  second,  and  also  for  stopping  the  car  in  1380  yds. 
Therefore,  either  of  the  brakes  used  alone  will  stop  the  car  in  that 
distance,  whereas  both  combined  will  stop  the  car  in  768  yds. 
This  does  not  take  into  account  the  steep  up  grades  at  the  stations. 

The  power  required  during  acceleration  is  about  1100  hp,  and 
during  the  run  about  515  hp,  or  129  hp  per  motor,  there  being  four 
motors  to  a  car. 

The  generating  station  is  situated  exactly  half  way,  at  Warring- 
ton.     Three-phase  currents  will  be  generated  at  15,000  volts  and 
converted  in  five  sub-stations  placed  along  the  line  into  continuous 
current  at  650  volts.     The  motors  are  wound  for  600  volts  and 
ELEC.  RYS. —  6. 


82  BEER:     MONORAIL  RAILWAY. 

weigh  each  about  2%  tons.  The  system  used  is  three-wire  con- 
tinuous current. 

Each  car  will  be  fitted  with  four  continuous  current  traction 
motors  arranged  in  pairs.  Each  motor  will  have  a  normal  capacity 
of  160  hp  at  the  full  speed  of  720  revolutions  per  minute,  but  will 
be  capable  of  giving  at  least  320  hp  for  short  periods  during  accel- 
eration. The  driving  wheels  have  a  diameter  of  4  ft.  4  in.,  the 
speed  at  720  revolutions  per  minute  corresponding  to  110  miles 
an  hour. 

The  whole  line  will  be  fenced  with  an  unclimbable  fence  from 
end  to  end,  preventing  all  possibility  of  trespassing,  as  there  are 
no  level  crossings  and  no  means  of  access  of  any  kind. 

By  an  arrangement  on  the  axles  of  the  guide  wheels,  which  are 
freely  suspended  in  slots  fixed  on  the  bogie  or  truck  frames,  the 
guide  wheels  on  both  sides  of  the  car  remain  always  horizontal  and 
in  fair  contact  with  the  guide  rails,  whatever  may  be  the  inclina- 
tion of  the  bogie  frames  and  the  car  itself,  which  can  swing  freely 
on  the  top  or  bearing  rail  under  the  influence  of  centrifugal  force 
in  the  curves,  or  from  any  other  causes.  The  main  rail  itself 
remains  always  perfectly  horizontal,  even  on  the  sharpest  curves. 
The  result  is  that  the  pressure  on  the  guide  rails  need  never  be 
increased  or  the  inclination  of  the  car,  and  this  pressure  can  be 
limited  in  such  a  manner  as  to  combine  the  greatest  comfort  of 
the  passengers  with  the  greatest  economy  in  electrical  energy 
through  the  diminution  of  friction, 


THE  ELECTRIFICATION  OF  STEAM  RAILROADS. 


BY  BION  J.  ARNOLD. 

Eleven  years  ago  this  summer  it  was  our  privilege  to  meet  under 
the  auspices  of  a  great  Exposition,  located  upon  the  shores  of  Lake 
Michigan,  organized  not  only  to  commemorate  the  400th  anni- 
versary of  the  discovery  of  this  country,  but  also  to  direct  atten- 
tion to  the  advancement  made  in  the  various  fields  of  the  world's 
activities,  and  especially  in  those  arts  in  which  we,  as  workers, 
were  most  interested. 

To-day  we  meet  under  the  auspice*  of  another  great  Exposition, 
brought  into  being  to  commemorate  the  100th  anniversary  of  the 
peaceful  acquirement  by  the  Government  of  the  United  States 
of  a  large  portion  of  the  territory  now  contained  within  its  bor- 
ders, to  have  our  attention  directed  to  the  development  of  the 
various  industries  of  this  and  other  countries  that  have  taken  place 
during  the  intervening  years. 

For  a  few  years  preceding  the  former  Exposition,  engineers  and 
others  engaged  in  electrical  pursuits  had  had  their  energies  ab- 
sorbed in  attempting  to  show  the  owners  of  street  railways  that 
operation  by  electricity  was  cheaper  and  better  than  by  means  of 
the  horse  or  the  cable.  We,  at  that  time,  had  seen  the  horse  prac- 
tically disappear  from  street  railway  service  and  the  cable  sup- 
planted in  some  instances. 

The  more  ambitious  engineers  were  then  advocating  the  use  of 
electricity  on  elevated  railways,  and  making  figures  to  prove  to 
the  owners  of  such  railways  that  electricity  was  cheaper  in  opera- 
tion and  more  desirable  for  such  conditions  than  steam  locomo- 
tives, then  universally  used  for  such  work. 

At  that  Exposition  was  placed  in  operation  an  elevated  electric 
road,  known  as  the  Columbian  Intramural  Kailway,  which,  though 
the  city  and  South  London  Underground,  a  road  of  light  equip- 
ment, was  started  some  time  before,  and  the  Liverpool  Overhead 
Eoad  soon  after,  was  the  first  practical  commercial  application  on  a 
large  scale  of  electricity  for  the  propulsion  of  heavy  railway  trains. 

[831 


84         ARNOLD:     ELECTRIFICATION   OF  STEAM   RAILROADS. 

The  success  of  these  roads  gave  the  electric  railway  industry  an 
impetus  which  has  since  resulted  in  the  abandonment  of  steam 
and  the  adoption  of  electricity  on  every  elevated  railway  now  in 
operation,  and  practically  on  all  of  the  underground  roads,  thus 
effectually  proving  the  soundness  of  the  theories  of  those  engineers 
who  pinned  their  faith  to  the  correctness  of  the  conclusions  which 
their  figures  showed,  and  who  staked  their  reputations  upon  the 
future  to  prove  them  true. 

The  interval  between  these  Expositions  has  also  been  one  of 
great  activity  and  development  in  the  field  of  interurban  railways, 
which  has  brought  into  being  the  extensive  use  of  the  alternating- 
current,  rotary-converter,  sub-station  system  of  operating  direct- 
current  roads,  resulting  in  the  interlinking  of  thousands  of  cities 
with  each  other  and  intervening  points,  thus  not  only  affording 
a  new  field  for  the  investment  of  capital  but  bringing,  to  most 
of  the  inhabitants  of  the  territory  through  which  these  roads  pass 
greater  facilities  for  the  prosecution  of  business  and  the  widening 
of  their  social  life. 

With  the  introduction  of  the  suburban  railway  came  an  increased 
volume  of  passenger  travel,  induced  by  the  increased  facilities, 
which  may  well  be  noted  by  the  managers  of  great  steam  railway- 
properties  as  an  example  of  what  may  be  expected  in  increased 
revenue  when  frequent  and  pleasant  service  is  available  to  the 
public. 

The  energies  of  those  engaged  in  electrical  industries  have  thus 
far  been  absorbed  in  fields  which  now  seem  to  have  been  naturally 
theirs,  and  their  success  has  been  such  that  they  now  aspire  to 
enter  the  field  occupied  by  the  steam  locomotive  as  a  legitimate 
field  of  conquest. 

The  questien  now  is  whether  this  field  is  one  in  which  the  ad- 
vantages of  electricity  will  be  sufficient  to  overcome  -the  obstacles 
which  seem  almost  unsurmountable,  and  enable  it  to  win  as  it  has 
in  the  cases  cited. 

Those  who  have  given  the  subject  little  thought  or  who  are 
unable  to  analyze  it  carefully  on  account  of  the  lack  of  the  tech- 
nical knowledge  necessary  to  appreciate  the  difficulties  to  be 
overcome,  are  most  apt  to  predict  the  early  supremacy  of  the 
electrically  driven  train  over  the  steam  locomotive. 

That  the  fields  referred  to  have  been  apparently  formidable 
yet  quickly  overcome  is  not  necessarily  proof,  or  even  good  evi- 


ARXOLD:     KLBCTRIFIGATION   OF  STEAM    RAILROADS.        85 

donee,  that  the  legitimate  field  of  the  steam  locomotive  can  be 
entered  and  successfully  achieved. 

Those  most  familiar  with  the  subject  are  now  prepared  to  admit 
that  our  great  steam  railway  terminals,  where  many  switching 
locomotives  are  shunting  back  and  forth  continuously,  and  those 
portions  of  the  steam  roads  entering  our  great  cities,  where  sub- 
urban trains  are  numerous,  frequent  and  comparatively  light,  can 
be  more  economically  operated  by  electricity  than  by  steam. 
This  is  evident  to  most  of  those  engaged  in  the  work,  for  the 
reason  that  it  simply  means  duplicating,  on  a  large  scale,  the 
systems  which  have  proven  successful  in  our  street  railways,  operat- 
ing, as  they  do,  numerous  units  running  at  frequent  intervals. 

Proof  that  this  field  is  recognized  as  a  legitimate  one  for  elec- 
tricity is  furnished  in  the  examples  of  steam  railway  terminals 
that  are  now  being  equipped  electrically,  such  as  the  lines  of  the 
New  York  Central  and  Pennsylvania  Eailroad  Companies  in  the 
vicinity  of  New  York,  involving  an  expenditure  of  something  over 
$70,000,000,  where  not  only  suburban  service  will  be  operated 
electrically,  but  where  in  the  case  of  the  New  York  Central,  the 
main  line  trains  will  be  brought  into  the  city  from  points  30  to  40 
miles  distant. 

While  these  are  great  examples  of  electrical  operation  on  steam 
railroads,  and  heroic  instances  of  faith  on  the  part  of  the  railway 
managers  in  the  ability  of  electricity  to  successfully  meet  the  con- 
ditions of  steam  railroad  work,  where  the  trains  are  sufficiently 
frequent,  they  are  by  no  means  conclusive  evidence  that  electrically 
propelled  trains  can  be  made  to  successfully  meet  the  conditions 
of  trunk  line  passengers  and  freight  service,  the  field  now  so  suc- 
cessfully held  by  the  steam  locomotive. 

The  best  conditions  for  electrical  success  are  a  great  number 
of  units  moving  at  a  practically  uniform  schedule,  at  equal 
intervals,  within  a  limited  distance. 

The  legitimate  field  of  the  steam  locomotive  is  now  one  in  which 
there  are  few  but  heavy  units  moving  at  uneven  speeds  over  long 
distances  at  unequal  intervals  and  at  high  maximum  speeds. 

The  amount  of  energy  transmitted  to  any  great  distance  and 
used  by  electric  cars  that  have  been  put  in  use  until  recently  has 
been  small  when  compared  with  the  amount  of  energy  that  it 
takes  to  propel  a  steam  railroad  train  of  five  or  six  hundred  tons 
weight  at  the  speeds  ordinarily  made  by  such  trains. 

It  may  be  taken  as  axiomatic  that  when  investment  is  taken 


80         ARNOLD:     ELECTRIFICATION   OF  STEAM   RAILROADS. 

into  consideration,  power  cannot  be  produced  in  a  steam  central 
station,  under  conditions  that  exist  to-day,  and  transmitted  any 
great  distance  to  a  single  electrically  propelled  train,  requiring 
from  1000  to  2000  hp  to  keep  it  in  motion,  as  cheaply  as  a  steam 
locomotive,  hitched  directly  in  front  of  the  train  will  pro- 
duce the  power  necessary  for  its  propulsion.  Therefore,  there 
must  be  other  reasons  than  the  expected  economy  in  power  prp- 
duction  to  warrant  the  adoption  of  electricity  on  a  trunk  line  rail- 
road unless  it  can  be  shown  that  the  trains  are  frequent  enough 
to  make  the  saving  in  the  cost  of  producing  power  greater  than 
the  increased  fixed  charges  made  necessary  by  the  increased  invest- 
ment due  to  the  adoption  of  electricity. 

There  are  undoubtedly  in  existence  to-day  conditions  where 
water  power  in  abundance  is  available  along  the  right  of  way  of 
existing  roads,  in  which  the  substitution  of  electricity  for  steam 
could  be  made  a  paying  one,  with  apparatus  now  available,  even 
on  roads  having  a  comparatively  infrequent  service,  but  these  are 
special  cases  and  only  tend  to  prove  the  correctness  of  the  position, 
for  in  these  special  cases  the  cost  of  power  would  be  but  little  over 
half  the  present  cost  of  producing  it  by  means  of  a  central  steam- 
driven  station. 

The  ideal  conditions  for  any  trunk  line  railroad  having  a  traffic 
heavy  enough  to  warrant  the  investment  in  a  sufficient  number 
of  tracks  to  properly  handle  this  traffic  in  such  a  manner  as  to 
get  the  most  efficient  service  out  of  its  rolling  stock,  would  be 
to  have  four  or  more  tracks  between  terminal  points,  upon  which, 
in  pairs,  could  be  run  the  different  classes  of  service  at  uniform 
rates  of  speed.  Thus,  if  six  tracks  were  used,  the  through  line, 
passenger,  and  express  service  would  be  run  on  one  pair  of  tracks ; 
the  local  passenger,  local  express,  and  local  freight  service  upon 
another  pair  of  tracks;  while  the  through  freight  service  would 
be  run  upon  a  third  pair  of  tracks,  and  all  the  trains  upon  any 
pair  of  tracks  would  run  at  the  same  average  speed  and  stop 
practically  at  the  same  places. 

If  these  conditions  could  prevail  and  the  traffic  were  sufficient 
to  warrant  this  investment  in  tracks,  such  a  service  could  be 
operated  more  economically  and  more  satisfactorily  electrically 
than  by  steam. 

The  difficulty  is  that  few  roads  in  existence  have  sufficient  traffic 
to  warrant  such  an  investment  in  a  permanent  way,  and  the  result 
is  that  all  of  their  traffic  must  be  handled  over  one  or  two  tracks. 


ARK  OLD:     ELECTRIFICATION   OF   STEAM    RAILROADS.        87 

thus  necessitating  trains  of  all  weights  and  all  speeds  running 
upon  the  same  rails.  This  results  in  a  tendency  to  bunch  the 
cars  into  as  few  trains  as  practicable,  in  order  not  only  to  reduce 
the  cost  of  train  service  to  a  minimum  but  to  give  the  fast-running 
trains  greater  headway  to  allow  them  to  make  their  time  safely. 
Such  an  arrangement  of  trains  necessitates  the  concentration  of 
large  amounts  of  power  in  single  units,  which  is  leading  away  from 
the  ideal  conditions  for  the  application  of  electricity  to  the  pro- 
pulsion of  trains;  and  it  is  this  element,  combined  with  the  fact 
that  the  traffic  on  most  roads  is  not  great  enough  to  warrant  the 
investment  necessary  in  electrical  machinery  to  produce  and  trans- 
mit the  power  to  the  distances  necessary  to  keep  a  few  heavy  trains 
in  motion,  that  makes  the  trunk  line  railway  problem  so  difficult, 
as  it  is  more  economical  to  propel  these  heavy  trains  by  steam- 
driven  locomotives,  which  are  practically  portable  power-houses. 

It  being  admitted  that  electricity  becomes  most  economical  when 
a  sufficient  number  of  trains  are  available,  and  that  the  steam 
locomotive  is  most  economical  when  the  trains  have  become  few 
and  heavy,  the  problem  then  resolves  itself  into  one  of  the  density 
of  traffic  and  the  question  then  is:  where  is  the  dividing  line? 

It  was  my  intention  to  attempt  such  an  analysis  of  this  subject 
as  to  be  able  to  formulate  some  general  law  which  could  be  readily 
applied  to  any  given  case,  and  thus  enable  one  to  decide  whether 
electrical  operation  would  be  more  economical  than  steam  in  any 
concrete  case. 

After  carefully  analyzing  the  subject  I  have  become  convinced 
that  no  general  law  or  formula  can  be  laid  down  which  will  apply 
to  all  cases,  for  the  reason  that  the  elements  entering  into  different 
cases  vary  so  greatly  that  any  formula  would  contain  too  many 
variables,  dependent  upon  local  conditions,  to  admit  of  a  general 
application. 

I  shall,  therefore,  only  attempt  to  point  out  a  way  in  which 
the  dividing  line  between  steam  and  electricity  can  be  determined 
after  the  elements  of  each  case  are  known. 

It  will  readily  be  seen  that  with  steam  locomotive  operation 
the  fixed  charges,  and  cost  of  fuel  and  engine  labor  increase  almost 
directly  proportional  as  the  train  miles  increase,  for  in  this  case 
an  additional  locomotive  means  simply  a  given  amount  of  increased 
investment,  a  given  amount  of  increased  fuel  and  labor,  and  this 
total  investment  is  least  when  the  number  of  locomotives  is  small. 

On  the  other  hand,  with  electricity  it  is  necessary  to  invest  at 


88        ARNOLD:     ELECTRIFICATION   OF  STEAM   RAILROADS. 

once  a  large  amount  of  capital  in  the  power  houses  and  trans- 
mission systems,  which  amount  must  be  great  enough  to  provide 
for  handling  the  maximum  number  of  trains  required  upon  the 
line,  and  unless  this  number  of  trains  is  great  enough  so  that 
the  economy  effected  in  the  different  method  of  producing  and 
applying  the  power  is  sufficient  to  offset  the  increased  fixed  charges, 
due  to  the  additional  invested  capital,  it  will  not  pay  to  equip 
and  operate  electrically. 

Any  problem,  therefore,  must  be  analyzed  for  the  relative  cost 
in  operation.  In  case  this  does  not  show  a  saving  the  advisability 
of  equipping  electrically  will  depend  entirely  upon  the  probable 
increased  traffic  to  be  derived  from  the  adoption  and  operation 
of  electrically  propelled  trains. 

That  electricity  will  be  generally  used  on  our  main  railway 
terminals,  and  ultimately  on  our  main  through  lines  for  passenger 
and  freight  service,  I  am  convinced,  but  I  do  not  anticipate  that 
it  will  always  be  adopted  on  the  grounds  of  economy  in  operation ; 
neither  do  I  anticipate  that  it  will  come  rapidly  or  through  the 
voluntary  acts  of  the  owners  of  steam  railroads,  except  in  special 
instances. 

At  first  the  terminals  will  be  equipped  for  special  reasons,  due 
either  to  the  voluntary  act  on  the  part  of  the  terminal  companies 
to  effect  economy  in  operation,  or  to  public  pressure  brought  to 
bear  upon  the  owners  through  an  increased  demand  on  the  part 
of  the  public  for  better  service,  on  the  grounds  that  the  use  of 
the  steam  locomotive  is  objectionable  in  our  great  cities. 

Those  roads  which  run  through  populous  countries  will  either 
build  new  roads,  or  acquire,  for  their  own  protection,  those  electric 
railways  already  built  and  operating  in  competition  with  them, 
and  utilize  them  as  feeders  to  their  through  line  steam  trains. 
Thus  the  steam  railroad  companies  will  gradually  become 
interested  in  electric  railways  and  eventually  become  practically 
the  real  owners  of  them.  With  these  roads  operating  as  feeders 
to  the  main  line  system  and  with  the  terminals  thus  equipped 
and  the  public  educated  to  the  advantages  of  riding  in  electrically 
equipped  cars,  the  next  step  will  logically  be  the  electrical  equip- 
ment of  the  trunk  lines  between  the  cities  already  having  electrical 
terminals. 

Thus  some  favorably  located  trunk  line  having  a  sufficient 
density  of  population  will  feel  warranted  in  equipping  electrically, 
and  when  this  is  once  done  the  other  roads  running  between  the 


ARNOLD:     ELECTRIFICATION   OF  STEAM   RAILROADS.        89 

same  competing  points  must,  sooner  or  later,  follow  in  order  to 
hold  their  passenger  traffic. 

This  may  result  in  temporarily  relegating  some  roads  to  freight 
service,  so  long  as  they  operate  exclusively  by  steam,  but  with  the 
increased  demand  on  the  part  of  the  public  for  better  and  cleaner 
service  will  come  a  corresponding  increase  in  passenger  revenue 
to  the  roads  equipped  for  handling  it  until  one  road  after  another 
finds  it  advantageous  to  furnish  an  electric  passenger  service. 

With  the  terminals  and  main  lines  equipped  electrically,  and 
the  desire  on  the  part  of  the  public  for  more  prompt  and  effective 
freight  service  resembling  that  which  is  given  by  the  steam  roads 
in  England  and  on  the  Continent,  due  to  the  great  density  of 
population,  there  will  be  developed  a  great  high-class  freight  serv- 
ice conducted  in  light,  swiftly  moving  electric  trains  which  can 
be  quickly  divided  and  distributed  over  the  surface  tracks  of  our 
smaller  cities,  or  through  underground  systems  similar  to  that 
which  is  now  being  built  in  Chicago.  Such  a  system  would  soon 
prove  indispensable  to  the  public  and  a  source  of  great  profit  to 
the  roads  as  it  is  now  getting  to  be  to  many  suburban  railways. 

This  class  of  freight  service  would  soon  prove  so  large  a  part 
of  the  freight  traffic  of  a  road  that  the  operation  of  the  through 
freight  traffic  by  steam  locomotives,  though  at  present  cheaper, 
would  in  time,  as  the  cost  of  coal  increases,  grow  less,  until  those 
roads  operating  an  electric  passenger  service  would  ultimately  use 
electricity  exclusively. 

It  has  not  seemed  advisable  to  me  in  an  address  of  this  char- 
acter to  attempt  to  furnish  detailed  figures  to  support  my  theories 
for  the  subject  is  of  such  general  interest  that  many  able  men 
are  presenting  papers  upon  it  at  the  International  Electrical  Con- 
gress now  in  session  here,  in  which  papers  will  be  found  informa- 
tion of  much  value  to  those  interested,  and  from  which  I  believe 
the  correctness  of  some  of  my  assumptions  can  be  proved. 

The  principal  problem  before  the  electric  railway  engineer  to-day 
is  how  to  make  the  most  effective  use  of  the  high-pressure  trans- 
mission, and  high-tension  working  conductor  and  maintain  safety 
of  operation. 

Experiments  conducted  during  the  past  year  by  engineers  in 
this  country  and  abroad  have  made  this  problem  simpler  than  it 
seemed  before  and  to-day  we  seem  reasonably  certain  of  the 
solution. 


f)0         ARNOLD:     ELECTRIFICATION   OF  STEAM   RAILROADS. 

Until  recently  the  cost  of  electrically  equipping  a  trunk  line 
under  the  standard  direct-current,  rotary-converter  system,  has 
been  such  as  to  practically  prohibit  its  adoption,  but  recent  devel- 
opments in  the  single-phase  alternating-current  motor  field  have 
made  it  possible  to  eliminate  a  large  part  of  the  investment  here- 
tofore necessary  and  the  prospects  for  the  application  of  electricity 
to  long-distance  running  are  better  than  ever  before. 

When  it  is  recalled  that  the  rotary  converter,  which  was  the 
means  of  reducing  the  cost  of  long-distance  roads,  was  introduced 
in  1898,  and  that  within  the  six  years  from  the  time  of  its  adop- 
tion through  the  development  of  the  single-phase  motor  it  has 
been  practically  rendered  obsolete  for  heavy  railroad  work,  it  will 
be  seen  that  the  dividing  line  between  the  steam  locomotive  and 
the  electrically  propelled  train  has  moved  several  points  in  favor 
of  the  latter,  due  to  the  reduction  which  can  now  be  made  in  first 
cost  and  the  saving  in  operating  expenses. 

With  the  single-phase  motor  and  the  steam-turbine  a  reality, 
the  transmission  problem  almost  solved,  and  with  the  rapid  devel- 
opment of  the  internal  combustion  engine  now  taking  place,  are 
we,  as  engineers,  not  warranted  in  believing  that  we  can  so  com- 
bine them  into  a  system  which  will  ultimately  supplant  the  steam 
locomotive  in  trunk  line,  passenger  and  freight  service? 

I  do  not  anticipate  that  all  roads  will  soon  adopt  electricity, 
for  the  steam  locomotive  will  hold  its  field  in  this  country  for 
many  years  to  come,  but  I  do  expect,  judging  somewhat  from 
"positive  knowledge,"  a  remarkable  development  to  soon  begin 
in  the  electrical  equipment  of  favorably  located  steam  roads. 

From  Richmond,  where  the  first  commercial  electric  road  was 
built,  to  the  present  is  but  17  years,  yet  within  that  time  the  horse 
has  been  relegated  to  the  past  as  a  serious  factor  in  transportation, 
the  cable  has  served  its  usefulness  and  awaits  its  end,  and  the 
suburban  railway  has  been  developed  and  is  now  rapidly  encroach- 
ing upon  the  field  of  the  steam  railroad. 

With  the  terminals  of  the  two  greatest  roads  in  the  United 
States  now  being  equipped  electrically  and  with  an  investment 
of  something  more  than  $4,000,000,000  in  electrical  industries 
made  within  a  quarter  of  a  century,  we  have  reason  to  feel  satisfied 
with  the  past. 

With  several  of  the  leading  roads  in  this  country,  of  England, 
of  Sweden,  of  Switzerland,  of  Italy,  and  Australia  electrically 
equipping  branch  lines  and  seriously  considering  changing  large 


ARNOLD:     ELECTRIFICATION   OF  STEAM   RAILROADS.        91 

portions  of  their  present  systems  from  steam  to  electricity,  we,  as 
personal  factors  in  this  great  industrial  advancement,  have  every 
reason  to  be  hopeful  for  the  future. 

DISCUSSION. 

PRESIDENT  EGBERT  KAYE  GRAY  :  I  do  not  know  whether  I  am  perfectly 
in  order  under  the  American  procedure  or  not,  but  our  habit  on  the  other 
•side,  when  we  receive  an  address  from  our  President,  is  to  tender  him  our 
thanks.  As  President  Arnold  has  said,  during  the  Paris  Exposition  we  had 
a  joint  meeting  of  the  two  Institutions,  and  I  am  very  glad  indeed  to  say 
that  we  have  in  this  hall  to-day  the  two  gentlemen  who  presided  on  that 
occasion,  namely,  Mr.  Carl  Hering  and  Professor  Perry. 

I  do  not  think  that  any  one  could  even  have  wished  to  criticise,  in  any 
way,  the  address  which  has  been  so  ably  given  by  your  President,  because 
if  any  man,  either  on  this  side  or  on  the  other  side  of  the  Atlantic,  is  pre- 
eminent in  connection  with  the  subject  he  has  treated,  I  think  it  is  President 
Arnold.  His  name  is  exceedingly  well  known  to  us  on  the  other  side,  and 
I  think  I  am  not  giving  away  any  secret  in  telling  you  that  the  evidence 
of  his  work  which  he  has  been  tendering  to  us  has  received  a  very  warm 
reception  there,  and  the  evidence  is  considered  to  be  the  best  that  can  be 
obtained  in  relation  to  the  matters  with  which  it  deals.  I  therefore  wish, 
in  the  name  of  the  Institution  of  Electrical  Engineers  of  Great  Britain,  to 
tender  to  my  colleague,  President  Arnold,  our  very  sincere  thanks  for  hit 
exceedingly  able  address ;  and,  with  your  permission,  I  will  ask  the  senior 
Past-president  of  the  Institution  of  Electrical  Engineers  of  Great  Britain 
to  second  the  motion — Colonel  Crompton. 

COLONEL  R.  E.  B.  CROMPTON  :  It  is  with  the  most  heartfelt  pleasure  that 
I  rise  to  second  the  motion  of  President  Gray,  that  the  thanks  of  the  Ameri- 
can Institute  of  Electrical  Engineers,  as  well  as  our  own  Institution  of 
England,  be  given  to  President  Arnold  for  his  address,  which  I  personally 
feel  is  worthy  of  this  great  occasion — the  meeting  of  the  two  Institutions. 

PRESIDENT  GBAY:  I  presume  it  is  unnecessary  to  put  this  motion  to  the 
meeting,  and  I  shall  put  it  by  acclamation  if  it  meets  your  approval. 

PRESIDENT  BION  J.  ARNOLD:  I  assure  you  that  your  expression  of  ap- 
proval is  very  much  appreciated  indeed. 

We  have  for  our  discussion  this  morning  a  subject  similar  to  that  which 
I  have  treated  in  my  address ;  in  fact  the  address  was  written  as  a  sort  of 
introduction  to  the  discussion  of  the  subject  entitled  "  Different  Methods 
and  Systems  of  Using  Alternating  Current  in  Electric  Railway  Motors." 
This  subject  has  received  the  attention  of  engineers  interested  in  electric 
railways  for  the  past  three  or  four  years.  During  the  past  two  years  it  has 
received  very  energetic  attention  on  the  part  of  leading  engineers  of  Europe 
and  this  country,  and  it  bids  fair  to  be  one  of  far  greater  importance  as  we 
:get  more  thoroughly  into  heavy  railway  work.  Since  I  have  talked  to  you 
quite  a  while,  notwithstanding  the  fact  that  my  name  appears  first  on  the 
program  to  discuss  the  question,  I  am  going  to  ask  a  gentleman  to  open  the 
discussion  who  is  one  of  the  most  distinguished  engineers  in  this  country, 
.and  one  of  the  most  distinguished  living  authorities  in  electrical  matters. 
I  have  the  pleasure  of  introducing  Dr.  C.  P.  Steinmetz,  of  the  General 


92        ARNOLD:     ELECTRIFICATION   OF  STEAM   RAILROADS. 

Electric  Co.  and  Past-president  of  the  American  Institute  of  Electrical 
Engineers. 

DR.  C.  P.  STEINMETZ:  The  problem  which  we  have  before  us  here  for 
discussion — the  problem  of  the  direct  application  of  alternating  currents  to 
electric  railways — is  not  a  new  one,  but  it  has  become  of  primary  importance 
and  interest  in  the  last  few  years.  The  early  pioneers  in  electric  rail 
roading,  10  or  15  years  ago,  started  the  development  of  the  alternating- 
current  railway  motor,  and  prominently  among  them  I  may  mention  Mr. 
R.  Eickemeyer  and  Mr.  Vandepoele,  who  designed  alternating  motors  for 
railway  purposes  and  investigated  their  characteristics.  However,  very 
little  progress  was  made  in  this  field  for  many  years,  for  a  number  of 
reasons;  one  being  that  in  those  early  days  frequencies  of  125  to  130  cycles 
were  customary,  far  higher  than  we  are  using  now  and  the  difficulties  of 
the  problem  were  thereby  increased  so  formidably  that  advance  was  neces- 
sarily very  slow.  In  addition  the  very  rapid  development  of  the  direct- 
current  railway  motor  fully  occupied  the  attention  of  all  electrical 
engineers,  and  therefore  the  less  urgent  field  of  the  alternating-current  motor 
was  necessarily  somewhat  sidetracked.  Then  the  alternating-current  poly- 
phase induction  motor  came  into  the  foreground,  showed  its  superiority 
over  other  types  of  motors  for  stationary  work,  and  impressed  the  engineers 
to  such  an  extent  that  for  a  long  time  it  overshadowed  the  work  done  by 
the  early  investigators  on  the  variable-speed  alternating- current  motor,  that 
is,  on  motors  with  series  characteristic.  Attempts  then  were  made  to  intro- 
duce this  very  successful  polyphase  induction  motor  into  electric  railway 
work,  attempts  which  have  not  been  successful  to  any  great  extent.  In  the 
meantime,  in  the  United  States  the  synchronous  converter  was  developed 
and  became  a  standard  piece  of  apparatus  familiar  to  everybody — standard 
as  much  as  the  direct-current  generator  and  the  alternating-current 
generator,  and  experience  with  such  synchronous  converters  shows  that  for 
electric  railway  work,  for  the  violently  fluctuating  loads  on  the  railway 
system,  the  synchronous  converter  is  superior  even  to  the  direct-current 
generator:  the  absence  of  armature  reaction,  the  phase  control  of  pressure 
feasible  in  the  converter,  and  corresponding  close  pressure  regulation  makes 
it  specially  able  to  withstand  and  take  care  of  very  violent  fluctuations  of 
load  and  to  carry  overloads  which  no  direct-current  generator  can  carry. 
This  apparatus  became  standard,  and  with  its  introduction  the  field  of  the 
direct-current  railway  motor — the  distances  which  could  be  covered 
by  the  direct-current  railway — was  extended  practically  without  limit,  and 
a  field  opened  which  has  been  exploited  in  the  last  years,  which  was  the 
field  dreamed  of  by  the  early  pioneers ;  the  difficulties,  however,  being  over- 
come, not  by  the  development  of  the  alternating-current  motor,  but  by  the 
development  of  methods  of  transmitting  alternating  currents  and  transform- 
ing them  into  direct  currents  along  the  routes,  in  synchronous  converter  sub- 
stations. 

Now,  however,  in  the  last  year  or  two,  with  the  still  further  development 
of  the  electric  railway  we  have  approached  and  in  many  instances  reached 
the  limits  of  applicability  of  this  synchronous  converter.  The  synchronous 
converter  is  a  piece  of  machinery  which  requires  sub-stations,  requires  some 
attendance,  and  as  a  necessary  result  has  a  high  economical  efncieney  only 


ARNOLD:     ELECTRIFICATION   OF  STEAM   RAILROADS.        93 

where  the  traffic  is  sufficiently  condensed  to  warrant  the  maintenance  of 
sub-stations  within  relatively  short  distances  from  each  other.  Where  the 
number  of  trains  is  less  or  the  power  per  train  greater  than  can  be  supplied 
at  500  volts  from  sub-stations,  without  excessive  expenditure  in  line  con- 
ductors, and  too  excessive  fluctuations  of  load,  pressures  are  required  higher 
than  can  be  utilized  efficiently  in  direct-current  motors,  and  there  we  strike 
the  limit  of  the  synchronous  converter,  and  the  alternating-current  motor 
has  to  come  in. 

Personally  I  do  not  believe  that  the  alternating-current  motor  will  make 
very  serious  inroads  in  the  field  now  occupied  by  the  direct-current  railway 
motor.  I  do  not  believe  that  direct-current  railway  systems  will  be  changed 
into  alternating-current  railway  systems;  but  what  I  expect  of  the  alter- 
nating-current railway  motor  is  that  it  will  find  a  field  of  its  own,  a  new 
field;  just  as  when  the  alternating-current  method  of  distribution  was 
developed  in  this  country,  it  did  not  displace  the  direct-current  method  of 
distribution  which  occupied  the  centers  of  our  large  cities,  but  it  found  a 
field  of  its  own,  a  field  which  has  gradually  developed  so  as  to  be  equal  in 
importance  if  not  superior  to  the  field  occupied  by  the  direct  current. 
Hence,  to  conclude  these  remarks,  what  I  expect  of  the  alternating-current 
railway  motor  is  that  it  will  find  and  develop  a  field  of  its  own,  that  field 
which  the  direct-current  railway  motor  cannot  reach — suburban  and  inter- 
urban  service,  long-distance  service,  secondary  railway  service. 

When  considering  the  technical  aspect  of  the  subject  before  us  for  dis- 
cussion to-day,  the  relative  advantages  and  disadvantages  of  the  direct-  and 
alternating-current  railway  motors,  we  have  to  consider,  first,  the  character 
of  the  problem  we  have  to  meet  in  electric  propulsion;  secondly,  the 
character  of  the  apparatus  which  we  have  available  to  solve  these  problems ; 
thirdly,  the  additional  features  imposed  upon  the  problem,  or  conditions 
more  or  less  outside  of  the  problem,  as,  for  instance,  the  condition  of  the 
electrical  industry  at  present,  the  existing  investment  in  direct-current  and 
in  steam  railroads,  which  have  to  be  taken  into  consideration  when  dis- 
cussing any  new  system  of  railway  propulsion. 

Regarding  the  characteristics  of  the  different  types  of  motors — the  direct- 
current  series  motor  now  in  universal  use  for  railroad  work,  the  polyphase 
induction  motor  proposed,  and,  to  a  certain  extent,  tried  in  recent  years 
for  railway  work,  a  motor  eminently  successful  in  stationary  work — and 
the  alternating-current  single-phase  railway  motor  with  commutator,  I  have 
in  a  paper  before  the  International  Electrical  Congress  given  the  results  of  a 
theoretical  investigation  and  discussion  of  these  different  motors  and  shown 
the  speed-torque  curves,  or  characteristic  curves  of  these  motors  in  relation 
to  each  other.  In  Fig.  1  is  given  a  comparison  of  the  typical  speed-torque 
curves  of  the  different  types  of  motors. 

In  general,  the  characteristic  of  the  polyphase  induction  motor  is  essen- 
tially that  of  a  constant-speed  motor,  with  shunt-motor  characteristics; 
that  is,  it  can  efficiently  operate  over  a  certain  limited  range  of  speed  only, 
cannot  exceed  the  synchronous  speed,  and  when  operating  below  its  normal 
speed,  it  operates  less  efficiently;  that  is,  when  operating  at  a  lower  speed 
than  normal,  or  approximately  synchronous  as  can  be  done  by  a  rheostat  in 
the  secondary  circuit,  the  polyphase  induction  motor  merely  wastes  that 


94        ARNOLD:     ELECTRIFICATION   OF  STEAM   RAILROADS. 

part  of  the  power  corresponding  to  the  difference  between  its  actual  speed 
and  synchronous  speed.  Or,  in  other  words,  at  low  speed  the  induction 
motor  consumes  the  same  power  which  it  consumes  with  the  same  torque  at 
full  speed,  though  its  power  output  is  reduced  in  proportion  to  the  speed, 
and  its  efficiency  correspondingly. 


Speed  Torque 
Characteristics 

of 
Railway  Motors 


FIG. 


In  the  direct-current  series  motor  the  torque  developed  by  the  motor  de- 
creases with  increase  of  speed,  and  inversely  with  increasing  load  the  speed 
of  the  motor  decreases.  The  maximum  torque  of  such  a  motor  occurs  in 


ARNOLD:     ELECTRIFICATION   OF  STEAM  RAILROADS.        95 

starting.  All  variable-speed  commutator  motors,  alternating  and  direct, 
more  or  less  differ  from  each  other  in  the  rate  at  which  the  torque  varies 
with  the  speed,  and  that  brings  us  to  a  consideration  of  the  requirements  of 
electric  propulsion. 

Important  classes  of  work  to  which  an  electric  motor  may  be  put  in  loco- 
motion are:  first,  city  railway  or  tram  car  work;  secondly,  rapid  transit 
service  as  on  elevated  and  underground  roads ;  thirdly,  suburban  and  inter- 
urban  service ;  fourthly,  trunk  line  passenger  service ;  fifthly,  long  distance 
freight  service,  and  sixthly,  elevator  service. 

Now,  discussing  these  briefly  in  succession.  The  city  tram  car  service  is 
characterized  by  its  frequent  stops  of  irregular  duration,  at  irregular 
intervals.  To  maintain  good  average  speed  it  is  therefore  essential  that  the 
motor  should  get  under  way  after  the  stop  as  rapidly  as  possible;  that  is, 
have  a  very  high  starting  torque  and  accelerating  torque,  and  carry  this 
high  torque  up  to  a  considerable  speed.  Beyond  this  speed,  then,  the  torque 
of  the  motor  should  decrease  fairly  rapidly  down  to  the  torque  required 
to  run  on  a  level  track,  which  we  may  assume  roughly  to  be  at  twice  the 
speed  to  which  the  high  torque  of  acceleration  should  be  maintained.  In 
addition  thereto,  it  is  necessary  that  the  motor  should  accelerate  efficiently 
and  that  it  should  be  able  to  operate  efficiently  at  low  speeds  in  those  city 
districts  where  the  general  traffic  is  dense  and  where  it  is  not  possible  to 
run  at  high  speeds.  The  characteristics  of  this  type  of  motor  are  pre- 
eminently given  by  the  direct-current  series  motor.  If  we  assume  the  torque 
required  to  run  on  a  level  track  as  1,  probably  the  starting  or  accelerating 
torque  may  be  something  like  six  times  as  high.  At  that  torque  we  start 
and  run  up  to  considerable  speed,  and  then  strike  what  is  called  the  motor 
curve  and  after  cutting  out  all  regulating  devices,  accelerate  with  decreas- 
ing velocity  up  to  the  free-running  speed.  Such  a  curve,  that  of  a  typical 
direct-current  railway  motor,  is  given  in  Fig.  1,  marked  "  direct-current 
parallel  "  and  "  direct-current  series."  The  induction  motor,  although  it 
may  accelerate  with  a  high  torque,  at  the  end  'of  acceleration,  the  speed  is 
limited.  It  accelerates  up  to  or  near  synchronous  speed,  and  there  the 
torque  falls  off  to  zero ;  and  hence  that  part  of  the  torque  curve  which  is  so 
essential  to  city  tramway  work,  the  curve  of  running  with  decreasing  torque, 
from  the  limit  of  acceleration  to  the  free-running  speed,  does  not  exist  in 
the  induction  motor.  We  can  indeed  reach  the  free-running  speed  of  a 
direct-current  motor  with  a  polyphase  induction  motor  by  gearing  it  to 
twice  the  speed,  making  synchronism  the  free-running  speed,  but  this  means 
that  the  available  torque  of  acceleration,  and  therefore  the  rate  of  getting 
under  way,  is  reduced  by  one-half,  or,  if  we  make  it  the  same,  the  motor 
capacity  is  twice  as  great,  requiring  a  motor  twice  as  large.  Considering 
that  in  this  service  a  very  considerable  part  of  the  running  time  is  occupied 
running  on  approximately  level  track  with  torque  very  small  compared  with 
the  accelerating  torque,  we  see  that  the  highest  possible  efficiency  of  the 
motor  at  light  load  is  essential.  Here,  however,  is  the  place  where  the  induc- 
tion motor  falls  down.  A  polyphase  induction  motor  running  at,  say,  one- 
tenth  of  its  maximum  output  runs  very  uneconomically  and  with  very  poor 
power-factor.  So  in  the  polyphase  induction  motor,  when  used  for  railway 
service,  you  cannot  combine  very  high  acceleration  with  high  efficiency  in 


06        ARNOLD:     ELECTRIFICATION   OF  STEAM   RAILROADS. 

free  running,  and  with  the  ability  of  running  efficiently  at  low  speeds,  aa 
you  can  in  the  direct-current  series  motor  with  series- parallel  control. 
Therefore,  the  induction  motor  is  not  suitable  to  the  class  of  work  which  we 
call  city  service  or  tram-car  work. 

The  alternating-current  commutator  motor  of  which  two  sets  of  curves 
are  shown  in  Fig.  1,  marked  "  alternating-current  parallel "  and  "  alter- 
nating-current series  "  has  characteristics  very  closely  similar  to  the  direct- 
current  railway  motor,  except  that  possibly  the  variation  of  torque  with 
the  speed  is  less.  That  means,  with  the  same  decrease  of  speed  the  torque 
does  not  increase  at  the  same  rate  as  with  the  direct-current  motor;  if  we 
assume  again  the  same  free-running  torque  as  1,  and  the  torque  of  accelera- 
tion six  times  the  free-running  torque,  the  direct-current  series  motor  will 
carry  the  acceleration  torque  up  to  half  speed ;  the  alternating-current  motor 
not  quite  as  high.  This  means  with  the  same  maximum  acceleration  you 
will  strike  the  motor  curve  at  a  lower  speed,  accelerating  on  the  motor 
curve,  you  get  under  way,  then,  slightly  slower,  or  to  get  the  same  average 
acceleration  you  have  to  start  with  a  higher  maximum  acceleration.  Now, 
this  is  an  advantage  in  some  cases  in  so  far  as  you  run  for  a  longer  period 
of  time  and  over  a  wider  range  of  speed  on  the  motor  curve,  that  is  without 
controlling  devices,  hence  in  the  most  efficient  manner  possible,  and  thereby 
make  up  to  a  considerable  extent  for  that  power  which  the  alternating- 
current  motor  inherently  loses  by  its  slightly  lower  efficiency  due  to  the 
alternating  character  of  the  magnetic  field,  and  the  losses  by  magnetic- 
hysteresis  in  the  motor  field  cf  the  alternating-current  motor  which  do  not 
exist  in  the  direct-current  motor.  This  difference  in  the  speed-torque  curve 
of  the  alternating-current  series  motor,  compared  with  the  direct-current 
series  motor,  is  due  to  the  lower  magnetic  density  used  in  the  alternating- 
motor  field,  and,  at  low  speeds,  also  to  the  e.m.f.  of  self-induction.  The  first 
phenomenon,  therefore,  also  occurs  in  an  unsaturated  direct-current  series 
motor  ( Fig.  1 ) ,  and  such  a  direct-current  series  motor  therefore  has  at  high 
and  medium  speeds,  the  same  characteristics  as  the  alternating-current 
motor.  It  is  undoubtedly  true  that  alternating-current  motors  can  be 
designed  to  give  very  closely  the  same  characteristics  as  the  standard  direct- 
current  series  motor.  However,  the  motor  as  it  is  before  us  at  present 
reaches  the  motor  curve  at  a  lower  speed,  therefore  with  the  same  maximum 
acceleration,  gives  a  lower  average  acceleration  up  to  full  speed,  or  with  the 
same  average  acceleration  requires  slightly  higher  maximum  acceleration. 

Coming  now  to  the  second  class  of  service,  rapid  transit  service,  here  the 
problem  and  the  conditions  of  operation  are  almost  identically  the  same  as 
in  city  service,  except  that  the  units  are  larger,  the  speeds  are  higher,  the 
stops  not  as  frequent,  absolutely,  but  about  just  as  frequent  relatively  in 
comparison  to  the  maximum  speed  of  the  motor,  so  that  we  can  directly 
apply  our  considerations  to  rapid  transit  service — regarding  a  comparison  of 
polyphase  induction  motors  of  alternating-current  commutator  motors,  and 
of  direct-current  motors. 

In  interurban  and  suburban  work,  that  is,  in  railroads  running  out  from 
the  cities  far  across  the  country  into  the  suburbs  or  into  other  cities,  we  have 
a  much  lesser  frequency  of  stops.  That  means  that  rapidity  of  acceleration 
is  of  lesser  importance,  and  we  can  well  get  along  with  a  lesser  average 


ARNOLD:     ELECTRIFICATION  OF  STEAM  RAILROADS.        97 

torque  of  acceleration,  but  we  must  have  the  same  surplus  torque  as  on  city 
service  work,  or  rather  a  greater  surplus  torque,  because,  while  in  city 
service  and  in  rapid  transit  service,  where  the  distances  are  relatively  short, 
we  can  count  on  maintaining  fairly  constant  pressure  in  the  supply  system, 
we  cannot  to  the  same  extent  count  on  this  in  interurban  and  suburban 
service  where  we  are  far  away  across  the  country,  except  by  investing  much 
greater  sums  in  line  conductors  and  feeders  than  is  commonly  economically 
desirable  or  feasible.  Hence,  in  this  service  the  motor  should  have  a 
greater  surplus  torque  than  in  city  service,  so  as  to  get  a  sufficient  margin 
to  start  the  train  or  the  car  under  the  most  severe  conditions  on  an  up- 
grade or  an  overload,  even  if  the  pressure  in  the  system  is  low.  The  motor 
which  is  most  sensitive  to  pressure  variation  is  the  polyphase  induction 
motor.  The  maximum  torque  which  this  motor  can  give  necessarily  cannot 
very  much  exceed  the  acceleration  torque  without  badly  spoiling  the 
characteristics  of  the  motor  either  electrically  or  mechanically;  but  the 
maximum  torque  varies  with  the  square  of  the  pressure  and  hence  rapidly 
decreases  if  the  pressure  of  the  system  is  low.  In  the  motors  with  series 
characteristics,  however,  like  the  single-phase  commutator  motor,  the  direct- 
current  series  motor,  the  torque  does  not  depend  on  the  pressure,  or  rather, 
while  the  maximum  torque  so  depends,  the  theoretical  maximum  torque 
which  you  get  from  the  motor  when  standing  still  is  so  far  in  excess  of  the 
torque  of  self-destruction,  or  rather  of  slipping  the  car  wheels,  that  it  is 
not  reached,  and  the  effect  of  variation  in  the  supply  pressure  is  merely  a 
variation  in  the  motor  speed.  That  is,  if  the  pressure  is  low  in  the  system, 
the  direct-current  motor  and  the  alternating-current  commutator  motor 
run  at  lower  speeds,  but  still  are  able  to  give  the  same  torque,  while  the 
polyphase  induction  motor  runs  at  the  same  speed,  but  is  not  able  to  give 
the  same  margin  of  torque,  and  at  a  certain  load  falls  down  or  does  not 
start.  That  means  that  in  designing  a  system  of  transmission  and  dis- 
tribution for  alternating-current  commutator  motors  or  direct-current 
motors  we  are  permitted  to  design  the  system  for  the  average  drop  of  pres- 
sure in  the  system  while  in  designing  it  for  induction  motor  service,  we 
have  to  take  into  consideration  the  maximum  drop  of  pressure  in  the 
system  which  is  very  much  greater  that  the  average. 

For  interurban  and  suburban  service  we  require  an  excess  overload  in 
torque,  but  do  not  require  an  acceleration  up  to  high  speed.  The  alter- 
nating-current commutator  motor  appears  to  be  preeminently  satisfactory 
in  this  work,  and  there  is  where  I  believe  it  will  be  used  extensively,  and 
where  the  advantage  of  a  high-pressure  trolley  and  of  the  absence  of  sub- 
stations is  specially  important. 

In  trunk  line  passenger  service  the  rate  of  acceleration  as  given  at  present 
by  the  steam  locomotive  is  very  much  less  than  every- day  practice  in  electric 
railway  service.  So  here  we  do  not  need  this  excess  acceleration  torque 
sustained  up  to  high  speeds.  Here,  again,  we  find  a  field  where  we  may 
apply  the  alternating-current  commutator  motors.  The  polyphase  induction 
motors  could  be  used  if  the  question  of  pressure  supply  did  not  come  in,  as 
I  discussed  above,  and  if  furthermore  the  limit  in  speed  of  the  induction 
motor  was  not  so  objectionable  in  passenger  trunk  service,  where,  more  than 
anywhere  else,  we  desire  to  get  the  full  benefit  of  the  track  by  running  at 

ELEC.   RYS. —  7. 


118        ARNOLD:     ELECTRIFICATION  OF  STEAM  RAILROADS. 

the  highest  safe  speeds  wherever  the  track  is  lerel.  This  the  induction 
motor  with  its  limited  speed  cannot  do. 

In  trunk  line  freight  service,  the  same  considerations  come  in,  except 
there  the  speeds  are  relatively  low,  the  train  weights  great;  and  it  is  more 
than  anywhere  essential  to  have  a  very  large  surplus  torque  available  to 
get  under  way  or  to  hold  the  train  on  a  grade.  You  must,  therefore,  in 
this  class  of  service,  just  as  in  suburban  and  interurban  service,  have  a 
motor  running  efficiently  at  light  load,  but  being  able  to  give  very  high 
torque,  although  it  does  not  need  to  carry  this  torque  up  to  high  speeds. 
On  the  contrary,  it  is  not  desirable  in  freight  service  that  the  motor  should 
sustain  a  high  torque  up  to  high  speeds,  because  that  would  mean  the  con- 
sumption of  very  large  power.  In  freight  service  the  highest  possible 
economy  is  especially  necessary,  and  the  highest  possible  economy  means 
the  least  fluctuations  of  power  consumption;  that  means  on  up-grades  you 
would  desire  to  go  slowly  and  reduce  the  power  consumption  and  get  the 
high  speeds  on  the  level  track. 

In  mountain  railways  and  such  classes  of  work,  the  running  torque  is  of 
the  same  magnitude  as  the  starting  torque,  and  so  the  load  on  the  motor 
is  more  nearly  constant  than  in  any  other  class  of  railway  work,  and  on 
the  down-grade  the  motor  is  preferably  used  for  braking,  by  returning  power 
into  the  line.  Here  then  the  polyphase  induction  motor  appears  well  suited, 
and  is  indeed  being  used  successfully.  Such  service,  however,  is  in  its 
character  more  nearly  akin  to  elevator  service  than  to  railway  service. 

In  the  discussion  so  far  I  have  considered  the  requirements  of  the  different 
classes  of  railway  service,  irrespective  of  extraneous  conditions.  When  con- 
sidering the  alternating-current  motor  and  the  direct-current  motor,  we 
have  to  take  in  view  what  exists  at  the  present  time  in  this  country  and 
abroad.  There  exists  the  enormous  network  of  steam  railroad  and  of  direct- 
current  electric  railways.  The  steam  locomotive  is  a  unit  of  very  high 
efficiency,  but  a  very  large  unit.  It  therefore  for  efficient  operation  requires 
the  massing  of  traffic  in  heavy  trains,  and  results  in  less  frequent  but  large 
trains.  This  has  practically  rearranged  and  reorganized  the  whole  system 
of  locomotion  by  collecting  it  into  a  small  number  of  very  large  units.  That 
is  not  the  most  efficient  manner  of  operating  electrically  propelled  vehicles, 
but  rather  the  contrary.  Furthermore,  you  have  to  consider  that  every 
city  and  almost  every  village  has  a  direct-current  railway  system.  Now, 
the  main  and  most  important  features  by  which  the  electric  railway  motor 
and  electric  propulsion  has  gained  and  is  gaining  rapidly  in  competition 
with  the  steam  locomotive,  appears  to  me  to  be  the  frequency  of  headway 
and  the  absence  of  passenger  stations,  not  the  speed,  which  frequently  in 
electric  lines  is  lower  than  that  on  steam  railroads  paralleled  by  them.  The 
electric  railway  picks  up  its  passengers  anywhere  in  the  city  and  deposits 
them  anywhere  and  it  does  not  require  them  to  consult  time  tables,  but 
runs  its  cars  so  frequently  that  the  passenger  can  always  find  a  car  within 
a  few  minutes  at  any  point;  on  the  other  hand,  the  steam  locomotive  re- 
quires you  to  consult  a  time  table  and  go  to  a  depot.  As  soon  as  the 
electric  railway  gives  up  this  advantage  which  I  have  just  mentioned,  I 
believe  one  of  the  main  advantages  of  the  electric  railway  over  the  steam 
railroad  will  be  lost,  and  this,  therefore,  is  the  feature  which  has  to  be  kept 


ARNOLD:     ELECTRIFICATION   OF  STEAM   RAILROADS.        99 

in  view.  It  means  that  whatever  type  of  motor  may  be  adopted  in  inter- 
urban  or  suburban  service,  etc.,  it  must  be  able  to  carry  the  passengers 
through  the  cities  over  existing  railways. 

The  existing  railways  are  direct-current  railways,  and  I  believe  will 
remain  so.  That  means  that  the  long-distance  motor,  at  least  the  sub- 
urban and  interurban  motor,  must  be  able  to  run  over  the  direct-current 
system.  Hence,  it  must  be  a  type  of  motor  equally  applicable  and  capable 
of  operation  on  a  high-pressure  alternating-current  or  on  the  500  volt  direct- 
current  system. 

Taking  this  for  granted  the  methods  of  control  must  also  be  as  simple  as 
possible;  that  is,  the  same  control  for  alternating  as  for  direct  current. 
Even  if  the  motor  could  be  used  on  direct  current  and  alternating  current, 
if  we  would  have  to  carry  a  double  system  of  control,  one  for  city  service 
and  direct  current,  the  other  for  long-distance  service  and  alternating  cur- 
rent, this  would  be  a  very  serious  handicap.  It  means  that  really  to  solve 
the  problem  before  us,  of  extending  the  electric  railway  into  interurban 
and  suburban  service,  and  into  the  field  now  occupied  by  the  steam  railroad 
systems,  and  into  new  fields  not  yet  developed,  to  a  large  extent  not  even 
dreamed  of,  that  we  must  have  a  motor  which  with  the  same  controlling 
appliances  and  the  same  characteristics,  can  run  either  on  the  high-pressure 
alternating  circuits  or  on  the  existing  direct-current  circuits. 

Furthermore,  the  enormous  investment  in  electric  railway  systems 
existing  at  present  has  all  been  made,  in  the  large  systems,  on  25-cycle, 
three-phase  apparatus.  That  means  that  we  shall  have  to  continue  to 
operate  at  25  cycles.  It  may  be  preferable,  possibly,  to  run  at  lower  fre- 
quencies, or  it  may  be  preferable  to  run  at  higher  frequency  in  this  instance 
or  that  instance,  but  regardless  of  whether  it  is  preferable  or  not,  if  it  can 
be  done  on  25  cycles,  it  will  have  to  be  done  on  25  cycles,  and  if  another 
frequency  had  to  be  used,  it  would  be  a  very  severe  handicap  to  the  new 
system.  I  am  glad  to  say  that  there  is  no  doubt  that  25  cycles  is  the 
frequency  best  suited  to  the  alternating-current  single-phase  railway  motor. 

PRESIDENT  GRAY:  Dr.  Steinmetz'  remarks  have  been  so  clearly  stated 
and  so  closely  reasoned  out  that  they  do  not  give  us  much  chance  for  dis- 
cussion, but  I  am  glad  to  refer  to  my  English  colleague,  Professor  John 
Perry,  upon  whom  I  call  to  take  part  in  this  discussion. 

PROFESSOR  JOHN  PERRY:  I  have  to  confess  that  1  am  not  prepared  to 
take  part  in  the  discussion.  We  have  had  the  address  of  President  Arnold 
and  this  excellent  address  of  Professor  Steinmetz,  and  two  such  addresses  in 
one  morning  I  think  we  have  never  had  before.  Clearly,  they  are  men  who 
have  thoroughly  studied  the  subject,  and  in  view  of  what  they  have  said,  I 
think  what  it  comes  to  is  this — that  everything  seems  to  depend  to  a  very  great 
extent  as  to  what  is  to  occur  in  connection  with  the  electrification  of  steam 
railroads  in  the  next  ten  years,  on  the  success  of  the  single-phase  alternating- 
current  motor.  I  knew  of  the  progress  that  had  been  made  by  the  General 
Electric  Company  and  the  Westinghouse  Company,  I  had  heard  a  great  deal 
about  it  before  leaving  the  other  side,  and  it  is  one  of  the  things  that  I 
promised  myself  to  learn  something  about  during  my  visit  here.  I  have 
not  yet  been  able  to  do  much  in  the  way  of  getting  accurate  knowledge  on 
the  subject.  I  have  been  on  a  tram-car  at  Schenectady,  the  motor  of  which, 


100      ARNOLD:     ELECTRIFICATION   OF  STEAM  RAILROADS. 

I  was  informed,  was  driven  by  direct  current  and  the  car  ran  well;  and 
then  I  would  get  on  another  car,  and  I  was  told  that  the  motor  was  driven 
by  alternating  current,  and  it  seemed  to  run  just  as  well,  so  that  I  was 
not  able  to  acquire  any  knowledge.  1  had  no  means  of  experimenting  or 
ascertaining  what  the  efficiency  of  the  various  arrangements  were.  Some 
10  or  12  years  ago  I  was  tremendously  interested  in  the  single-phase  alter- 
nating-current motor,  perhaps  for  a  selfish  interest,  as  I  had  invented  a  sys- 
tem of  traction  which  required  the  use  of  that  system.  I  suppose  we  are 
all  tremendously  interested  in  this  thing,  and  are  all  anxious  to  learn  what 
we  can  about  the  alternating-current  motor.  I  wanted  to  go  to  the  section 
in  which  Mr.  Steinmetz  was  giving  an  account  of  the  work  yesterday,  but 
I  was  told  it  was  my  duty  to  attend  a  discussion  upon  the  subject  of  electro- 
magnetic units  in  another  section,  and  as  a  man  cannot  be  in  two  places  at 
once,  I  had  to  attend  to  my  duty  as  it  was  pointed  out  to  me.  In  these 
circumstances,  I  can  only  say  that  I  should  like  to  hear  the  discussion  of 
this  subject  proceed  further  before  I  shall  feel  able  to  take  any  part  in  it. 

PBESIDENT  AENOLD:  It  has  been  said  that  the  fame  of  a  scientific  man 
is  a  quiet  fame,  but  that  is  the  most  satisfactory  after  all.  It  does  not 
attract  the  multitude.  A  man  is  able  to  walk  in  a  crowd  without  being 
pointed  out,  which  by  the  way,  is  a  very  satisfactory  thing  to  do;  but  he 
finds  that  when  he  reaches  different  parts  of  the  world  his  name  has  pre- 
ceded him  in  the  circles  in  which  he  moves,  so  that  he  after  all  enjoys  in 
the  most  satisfactory  way  the  results  of  his  efforts  in  the  particular  line 
of  work  which  he  has  been  following.  We  have  many  such  men  present 
to-day,  and  among  them  is  one  who  has  done  excellent  work  in  the  special 
line  we  are  discussing  this  morning.  I  shall  now  call  upon  one  of  our  dis- 
tinguished engineers  and  colleagues,  Mr.  B.  G.  Lamme,  of  the  Westinghouse 
Electric  &  Manufacturing  Co.,  of  Pittsburg,  to  discuss  the  question  further. 

MB.  B.  G.  LAMME:  Away  back  in  the  dark  ages  of  electric  traction, 
about  15  years  ago,  there  was  great  confusion  in  the  types  of  apparatus 
used.  There  were  all  kinds  of  motors  and  all  kinds  of  apparatus  on  the 
car.  They  only  had  one  property  in  common — they  were  all  direct-current. 
After  putting  a  number  of  these  systems  into  commercial  use  it  was  dis- 
covered that  certain  types  of  apparatus  were  superior  to  others,  and  those 
particularly  interested  in  the  manufacture  of  such  apparatus  followed  up 
this  matter  to  ascertain  what  properties  were  of  the  greatest  value.  It  was 
gradually  discovered  that  one  type  of  motor  was  taking  precedence  of  all 
others,  namely,  the  series  motor.  Practically  all  development  for  a  certain 
time  was  in  the  direction  of  the  direct-current  series  motor. 

The  reasons  which  led  to  this  were  partly  based  on  theory  and  partly  on 
practice.  The  series  motor  gave  the  effect  of  a  cushion  on  a  car.  The  motor 
is  inherently  a  variable-speed  machine  and  automatically  varies  its  speed 
with  the  condition  of  the  load.  That  was  discovered  to  be  a  matter  of  first 
importance  in  the  smooth  operation  of  electric  cars.  Also  the  motor  auto- 
matically increases  its  torque  in  a  greater  proportion  than  the  current, 
which  is  of  great  importance  in  regard  to  starting  and  acceleration.  These 
points  were  possibly  not  as  well  understood  at  that  time  as  at  present,  but 
experience  showed  that  certain  equipments  were  superior  to  others  and 
development  was  along  that  line. 


ARNOLD:     ELECTRIFICATION   OF  STEAM   RAILROADS.       101 

.After  a  few  years,  when  the  motors  had  reached  standard  proportions 
and  practically  but  one  type  was  used,  a  second  limitation  was  discovered ; 
namely,  in  the  transmission  conditions.  It  was  found  that  in  the  extension 
of  the  railway  system,  the  ordinary  550-  or  600-volt  direct-current  system 
was  becoming  cumbersome,  and  it  was  evident  that  some  method  of  trans- 
mitting power  at  higher  pressure  and  transforming  to  lower  pressure  for 
utilization  would  be  necessary.  The  most  evident  method  was  naturally  to 
transmit  by  alternating  current  and  convert  to  direct  current,  in  order  to 
use  existing  car  equipment.  This  led  to  the  use  of  motor-generators,  and 
later  to  synchronous  converters. 

The  motor-generator  was  found  to  fit  the  existing  alternating  system 
fairly  well,  but  in  the  development  of  the  synchronous  converter  the  manu- 
facturers discovered  a  great  difficulty  in  existing  systems.  The  frequencies 
of  125  and  133,  which  were  the  standards  for  many  plants,  were  entirely 
unsuited  for  synchronous  converters  and  also  not  well  adapted  for  synchro- 
nous motors.  Another  frequency,  coming  into  general  use,  namely,  60 
cycles,  was  found  to  be  possible  for  use  with  synchronous  converters,  but 
the  difficulties  of  design  were  very  great  in  that  case,  and  the  synchronous 
converters  were  rather  heavy  and  cumbersome. 

At  that  time  there  was  fortunately  a  new  frequency  adopted  which  was 
of  prime  importance  in  the  development  of  the  synchronous  converter, 
namely,  25  cycles.  So  far  as  I  know,  the  origin  of  that  on  a  large  scale, 
was  as  follows :  in  the  Niagara  Falls  power  plant,  when  it  was  first  laid  out, 
the  engineers  for  the  power  company  had  arranged  for  a  frequency  of  2000 
alternations  per  minute,  or  16%  cycles  per  second.  They  wished  to  use 
8-pole  machines,  running  at  250  revolutions.  The  company  which  I  repre- 
sent, which  was  one  of  the  prominent  bidders  on  the  contract,  objected 
seriously  to  the  proposed  frequency,  as  it  was  considered  entirely  uncom- 
mercial and  also  not  suited  for  the  best  design  of  machine.  The  engineers 
of  this  company  recommended  4000  alternations  per  minute  or  33%  cycles 
per  second.  That  was  considered  extremely  low  compared  with  anything 
then  in  use.  As  we  could  not  come  to  any  agreement  to  use  that  frequency, 
we  finally  compromised  on  3000  alternations  per  minute,  or  25  cycles  per 
second,  and  the  first  Niagara  machines  were  built  in  that  way.  There  were 
various  reasons  for  the  adoption  of  a  low  frequency,  one  of  which  was  that 
commutator  type  of  motors  might  possibly  come  into  use.  Another  reason 
was  that  it  was  better  adapted  to  synchronous  converters,  but  it  was 
admitted  that  33%  cycles  would  also  be  satisfactory. 

After  the  Niagara  Falls  plant  was  installed,  there  was  then  a  precedent 
for  the  adoption  of  this  frequency  for  large  units,  and  the  manufacturers 
began  to  build  apparatus  of  this  frequency  for  the  Niagara  Falls  plant  and 
also  adopted  it  for  other  plants.  This  opened  quite  a  field  for  the  synchro- 
nous converter  and  it  soon  began  to  be  extensively  used  for  railway  work, 
as  it  was  recognized  that  this  was  the  link  needed  for  extending  the  direct- 
current  system.  Even  at  the  early  date  of  1893  and  1894  it  was  believed  by 
many  engineers  that  the  synchronous  converter  was  simply  a  machine  to 
meet  an  emergency  condition,  that  it  would  not  last,  that  the  time  would 
oome  when  synchronous  converters  would  be  dropped  from  the  railway 
service,  but  as  the  most  convenient  and  apparently  the  best  solution  of  the 


102      ARNOLD:     ELECTRIFICATION   OF  STEAM   RAILROADS. 

problem,  it  was  adopted  extensively.  About  that  time  electric  railway 
service  began  to  be  greatly  extended  and  synchronous  converters  have  thus 
come  into  very  general  use.  By  the  use  of  synchronous  converters,  the 
advantages  of  the  alternating-current  system  in  transmission  are  obtained 
and  the  advantages  of  the  direct-current  system  with  the  series  motor  are 
retained.  Distances  could  be  extended  indefinitely  by  increasing  the  number 
of  synchronous  converter  stations  and  raising  the  pressure  of  the  alter- 
nating-current lines. 

Shortly  after  this  system  came  into  general  use  it  was  recognized  that 
a  purely  alternating-current  system,  in  which  purely  alternating  current 
was  supplied  to  the  motors,  would  be  advantageous  and  considerable  work 
was  done  along  that  line.  The  polyphase  motor  apparently  had' the  field, 
and  naturally  the  manufacturing  companies  took  up  the  question  of  the 
application  of  the  polyphase  motor  to  traction  work.  The  company  which  I 
represent,  the  Westinghouse  Electric  &  Manufacturing  Company,  took  up 
this  question  in  an  active  way  about  1895,  and  built  two  motors  of  75  hp 
each  for  traction  work.  These  motors  were  equipped  with  collector  rings 
and  rheostatic  control  and  tests  were  made  in  regard  to  performance,  both 
with  straight  rheostatic  control  and  with  the  new  well-known  "  tandem  " 
control,  in  which  the  secondary  of  one  motor  is  connected  to  the  primary 
of  the  other  to  obtain  half-speed  conditions.  Even  with  this  latter  arrange- 
ment it  was  found  that  the  motors  would  not  compare  at  all  favorably  with 
the  direct-current  motor  or  the  system  with  the  direct-current  system  using 
rotary  converters,  and  this  work  was  abandoned.  It  was  recognized  that 
the  polyphase  motor  did  not  possess  the  proper  series  characteristics  which 
long  experience  had  shown  to  be  so  necessary  for  railway  work.  Other 
experiments  along  this  line  were  made,  using  polyphase  motors  wound  for 
two  or  more  speeds,  and  two  100-hp  motors  were  built  which  were  wound 
for  several  speeds.  While  this  was  better  than  the  other  arrangements,  it 
still  appeared  that  this  was  not  a  solution  of  the  problem.  Previous  to 
this  time  the  company  had  done  some  work  in  the  direction  of  using  single 
phase,  but  not  as  a  solution  of  the  problem  which  presented  itself  in  1895 
and  later. 

In  1892  the  question  of  the  use  of  the  commutator  type  alternating-cur- 
rent motor  for  railway  work  was  taken  up.  Two  motors  of  nominally  10 
hp  each  were  designed  and  built.  These  were  built  for  a  frequency  of  2000 
alternations  per  minute,  or  16%  cycles  per  second.  They  were  mounted  on 
a  car  and  were  operated  for  awhile,  but  the  system  was  not  a  success.  In 
the  first  place  the  pressure  used — 400  volts  as  compared  with  550  in  the 
direct-current  motor — was  rather  low.  It  was  considered  that  as  550  volts 
was  the  limit  in  the  direct-current  motor,  400  volts  would  be  the  limit  with 
alternating  current.  The  motors  were  tested  on  a  track  of  iron  rails  with 
practically  no  bonding.  The  track  drops  were  excessive  and  the  pressure 
fluctuations  were  great.  The  generator  used — of  about  20  kw  capacity — 
was  entirely  too  small  for  this  work  and  it  was  not  adapted  to  handle  the 
inductive  loads  which  were  found  with  alternating-current  motors.  A 
series  of  tests  was  run  and  it  was  finally  decided  that  for  city  work,  for 
which  the  system  was  then  laid  out,  the  motor  could  not  compete  with  the 
direct-current  motor.  It  was  decided,  however,  that  such  a  type  of  motor 


ARNOLD:     ELECTRIFICATION   OF  STEAM   RAILROADS.      103 

would  probably  furnish  the  solution  of  the  heavy  railroad  problem,  but  as 
there  was  no  such  heavy  railroad  problem  at  that  time,  the  work  was 
dropped  for  awhile.  But  in  1897  the  question  of  the  use  of  the  commutator 
type  of  alternating- current  motor  was  again  taken  up — this  time  on  a  some- 
what larger  scale.  Motors  of  50  hp  were  built  for  variable-speed  work, 
and  given  a  long  series  of  tests.  Then  after  sufficient  experience  had  been 
obtained,  the  work  was  gradually  carried  to  the  larger  sizes. 

In  1900  and  1901,  when  the  question  of  the  polyphase  traction  in  Europe 
was  so  extensively  advertised,  it  became  evident  that  there  was  actually  a 
demand  for  an  alternating- current  railway  system.  It  was  therefore  decided 
to  continue  the  previous  work  with  large  motors  of  the  commutator  type, 
and  two  motors  of  100  hp  were  designed  and  built.  For  these  also,  the 
frequency  adopted  was  2000  alternations  per  minute,  or  16%  cycles  per 
second.  This  fractional  figure  was  primarily  adopted  on  account  of  certain 
steam-engine  conditions.  It  was  recognized  that  an  even  frequency  of  16  or 
18  would  have  been  practically  as  good. 

In  the  earlier  work,  with  the  10-hp  motors  at  the  low  frequency,  it  was 
recognized  that  it  would  be  absurd  to  put  such  a  system  on  the  market,  as 
at  that  time  even  25  cycles  had  not  been  adopted.  The  frequencies  in 
common  use  were  50  or  60  and  a  drop  to  16  cycles  was  considered  pro- 
hibitive. In  the  latter  work,  as  25  cycles  had  come  into  general  use,  and 
15  or  20  cycles  had  been  talked  of  and  proposed  by  certain  companies,  it 
was  considered  that  in  view  of  their  advantages  for  railway  work  such  fre- 
quencies should  be  adopted.  The  motors  were  hence  built  for  the  above 
frequency.  The  results  obtained  with  these  large  motors  were  so  satis- 
factory that  a  contract  was  taken  for  a  rather  large  road  and  the  apparatus 
prepared.  Knowing  that  news  of  this  would  soon  be  abroad,  it  was  decided 
that  the  matter  should  be  brought  before  the  American  Institute  of  Elec- 
trical Engineers,  and  a  paper  was  presented  on  the  26th  of  September — two 
years  ago — which  I  believe  was  the  first  announcement  of  the  application 
of  the  single-phase  alternating  current  to  railway  motors.  There  was  con- 
siderable discussion — mostly  criticism — and  it  was  generally  considered  by 
the  engineering  public  that  the  weak  point  of  the  system  was  the  commu- 
tation. At  the  present  time,  however,  I  believe  this  is  no  longer  considered 
as  a  serious  point. 

Previous  to  building  the  100-hp  motors  we  had  had  considerable 
experience  with  the  commutation  of  such  motors.  Besides  a  long  series  of 
tests,  we  had  run  40-hp  motors  at  practically  full  load  on  a  60-cycle  sys- 
tem for  nine  months,  day  and  night.  At  the  end  of  the  nine  months  the 
commutators  were  in  practically  as  good  condition  as  in  the  beginning, 
showing  that  the  commutator  on  such  machines  could  be  made  to  have  a 
long  life.  The  conditions  of  the  60-cycle  machines  were  much  worse  than 
on  the  lower  frequency,  and  the  nine  months  of  operation  under  the  con- 
dition of  steady  service  probably  equalled  two  or  three  years  of  traction 
service;  but  the  commutator  stood  up  so  well  that  we  decided  definitely 
that  there  was  no  difficulty  on  that  point. 

The  principal  reasons  which  led  to  the  adoption  of  the  single-phase  motor 
were  stated  in  the  paper  above  referred  to,  and  were  that  but  one  trolley 
wire  would  be  required  and  that  the  motors  had  the  series  characteristics. 


104      ARNOLD:     ELECTRIFICATION  OF  STEAM   RAILROADS. 

It  was  considered  that  no  motor,  except  one  of  the  commutator  type  would 
give  suitable  characteristics  for  the  service,  and  it  was  stated  that  there 
were  several  types  of  motors,  with  commutators,  which  had  the  proper 
characteristics.  All  of  these  may  be  classed  as  series  motors,  although 
some  of  them  are  combined  with  transformers  and  may  be  considered  as 
transformer  series  motors,  or,  under  another  name,  as  repulsive  motors, 
and  others  are  pure  series  motors.  The  pure  series  motor  is  one  which 
can  operate  on  direct  current  as  well  as  alternating  current.  The  repulsion 
motor  can  be  modified  so  as  to  operate  on  direct  current,  but  as  ordinarily 
arranged  it  is  not  as  well  adapted  for  this  as  the  other  type.  It  was 
recognized  in  the  first  undertakings  with  this  system  that  the  motor  would 
probably  be  required  to  operate  on  direct  current  at  times,  and  the  fact  that 
the  pure  series  motor  was  primarily  a  direct-current  motor  of  a  first-class 
design  was  one  of  the  reasons  which  led  us  toward  the  adoption  of  that 
type.  As  both  theory  and  experience  indicated  that  such  motors  would 
probably  be  wound  for  200  or  250  volts,  it  was  recognized  that  the  motors 
would  probably  have  to  be  operated  in  series  for  direct  current,  and  either 
in  series  or  in  parallel  for  alternating  current  as  might  be  desired.  The 
arrangement  required  for  permitting  operation  on  direct  current  as  well  as 
alternating  are  rather  complicated,  due  to  the  fact  that  it  is  necessary  to 
switch  from  one  system  to  the  other  in  passing  from  the  alternating  to  the 
direct  current.  We  did  not  suppose  that  the  electrical  public  would  con- 
sent to  such  a  combination,  but  since  that  time  we  have  found  that  in  some 
instances  they  do  not  object  seriously  to  the  increased  complication. 

At  the  time  that  the  alternating-current  system  was  brought  out  it  was 
considered  that  the  principal  field  would  be  in  heavy  railway  work,  because 
this  motor  furnished  what  was  considered  a  general  solution  of  the  railway 
problem;  as  the  railways  would  have  their  own  terminals  and  their  own 
rights  of  way,  the  system  would  be  an  alternating-current  system  through- 
out. At  the  present  time,  however,  roads  are  being  installed  which  operate 
primarily  on  alternating  current,  but  at  the  terminals  and  where  they 
pass  through  intervening  towns  they  operate  on  direct  current. 

The  direct-current  motor  has  never  been  considered  as  entirely  suitable 
for  the  heavy  railway  problem,  as  usually  but  two  speeds,  and  at  most 
but  three  speeds  can  be  obtained  with  four  motors,  the  third  speed  increas- 
ing the  complication  considerably.  With  the  alternating-current  motor  of 
the  commutator  type  any  speed  can  be  obtained  for  locomotive  work,  because 
any  pressure  can  be  applied  to  the  terminals  of  the  motor.  As  soon  as 
alternating  current  is  used  for  motors,  we  at  once  have  a  ready  means  of 
pressure  transformation.  As  on  locomotives  for  large  capacity  the  diffi- 
culty of  handling  the  current  is  considered  a  very  prominent  one,  it  was 
considered  that  some  form  of  pressure  control  which  varied  the  pressure 
without  opening  the  circuit  would  probably  be  the  best  one.  One  form  of 
pressure  control  permissible  is  what  is  called  the  induction  regulator.  This 
regulator  varies  the  pressure  without  opening  the  circuit.  The  relation  of 
the  primary  and  secondary  windings  with  respect  to  each  other  is  varied. 
This  gives  a  means  of  varying  the  pressure  to  the  motors  and  varying  the 
speed  of  very  large  motors  with  no  tendency  to  sparking  at  the  controller. 
The  only  time  the  circuit  is  opened  is  at  the  end  of  the  operation  when 


ARNOLD:     ELECTRIFICATION  OF  STEAM   RAILROADS.      105 

cutting  it  off.  Therefore  it  was  considered  as  an  important  feature  in  the 
solution  of  the  general  railway  problem. 

The  single-phase  system  is  the  one  means  presented  at  the  present  time 
as  the  solution  of  the  heavy  railway  problem.  It  has  all  the  advantages 
of  the  direct-current  motor  in  the  variable-speed  characteristic,  and  has 
also  the  advantage  possessed  by  alternating  current  in  the  ability  to  use 
any  line  pressure  desired,  and  to  vary  the  pressure  applied  to  the  motor 
and  thus  vary  the  speed  over  any  range  desired.  It  also  has  the  advantage 
of  permitting  a  system  of  control  that  can  be  obtained  without  sparking. 

In  the  adaptation  of  the  alternating- cur  rent  motor  to  direct-current  serv- 
ice, two  250-volt  motors  can  be  connected  in  series  for  500  volts;  also  in 
operating  on  alternating  current  the  motors  can  be  connected  in  series,  if 
desired,  or  in  parallel.  There  is  a  possibility  of  danger  in  operating  two 
motors  in  series  in  this  way  on  alternating  current,  or  even  on  ordinary 
direct  current.  In  ordinary  direct-current  practice  the  use  of  two  motors 
in  series  for  part  of  the  service  is  common  practice,  but  there  is  this  differ- 
ence between  the  direct-current  equipment  and  the  alternating-current  equip- 
ment. In  the  direct  current  we  have  motors  wound  normally  for  500  or 
600  volts.  When  operating  in  series  the  motors  are  connected,  two  in 
series,  each  one  receiving  250  volts.  Therefore,  if  one  motor  should  slip  its 
wheels  and  take  the  full  pressure  of  the  pair,  it  would  still  be  operating 
at  its  normal  pressure.  But  with  two  250-volt  motors  connected  across  a 
500-volt  circuit,  we  have  a  different  condition.  In  case  one  motor  should 
take  the  entire  pressure,  we  should  have  500  volts  across  a  250-volt  motor. 
That  condition  was  considered  early,  and  in  the  Washington,  Baltimore, 
Annapolis  project,  a  description  of  which  was  given  in  the  American  Insti- 
ture  paper  read  two  years  ago,  we  showed  an  arrangement  by  which  this 
could  be  avoided.  We  had  balancing  transformers  connected  across  the  two 
motors  in  series.  The  balancing  transformer  was  across  the  outside 
terminals,  and  a  tap  from  the  middle  of  the  transformer  was  connected 
between  the  two  motors.  In  this  way  equal  pressure  was  supplied  to  the 
two  motors  in  series,  and  the  danger  of  a  runaway  was  thus  avoided.  It 
is  not  yet  determined  how  important  this  is,  but  I  believe  that  something 
like  this  will  be  found  advisable  for  the  operation  of  motors  in  series, 
especially  where  high-power  motors  are  used  on  medium  weight  cars  for 
high-speed  service.  Possibly  with  comparatively  low  speed,  and  with  very 
heavy  cars,  there  may  not  be  the  same  tendency  to  slip.  On  the  direct- 
current  part  of  the  road,  of  course,  the  balancing  transformer  could  not 
have  any  effect;  but  as  the  direct  current  is  usually  a  very  small  part  of 
the  service,  this  danger  would  be  lessened,  due  to  the  proportionate  time  in 
service. 

In  the  application  of  the  motor  to  use  on  both  alternating  and  direct 
current,  we  have  found  some  special  conditions  which  affect  the  arrange- 
ment of  control.  Take,  for  instance,  a  large  road  being  installed  between 
Cincinnati  and  Indianapolis,  where  it  is  intended  to  run  on  direct  current  at 
the  terminals  and  alternating  current  on  the  rest  of  the  line.  The  normal 
speed  on  the  alternating  current  part  of  the  line  is  so  great  that  it  would 
be  prohibited  in  the  towns,  and  it  is  found  that  to  get  the  speed  down  to 
the  desired  rate  in  the  city  service  on  the  direct-current  portion  of  the  road, 


106      ARNOLD:     ELECTRIFICATION  OF  STEAM  RAILROADS. 

it  is  necessary  to  connect  the  four  motors  all  in  series,  and  thus  no  series- 
parallel  arrangement  can  be  used.  Pure  rheostatic  control  is  therefore 
necessary  in  the  city.  On  the  suburban  part,  a  switch  is  used  to  throw  the 
current  from  direct  to  alternating,  simply  throwing  the  four  motors  in 
parallel,  and  taps  are  used  on  the  lowering  transformers  to  get  a  number 
of  pressures.  In  that  way  we  get  the  effect  of  series-parallel  control  and 
even  better,  by  having  more  than  two  steps.  On  a  long  line  it  is  possibly 
of  no  great  advantage  to  have  many  steps,  but  as  a  rule  the  more  steps 
there  are,  the  easier  is  the  service  on  the  controlling  apparatus,  and  the 
more  running  speeds  are  available. 

With  regard  to  the  application  of  the  system  to  locomotives,  on  the  steam 
roads  where  the  systems  are  not  tied  up  with  existing  electric  plants,  it  is 
probable  that  in  time  the  railroads  will  adopt  their  own  pressures,  and 
possibly  their  own  frequency.  This  may  not  be  25  cycles  but  may  be  some- 
what lower.  I  believe  that  the  electrification  of  the  steam  road  may  be  a 
controlling  factor  in  the  change  from  direct  to  alternating  current  in  city 
service.  If  the  large  railroads  with  their  own  large  power  plants  adopt 
alternating  current  throughout,  then  the  towns  lying  along  the  roads  will 
in  time  probably  adopt  the  same  power  system,  and  even  the  large  cities 
will  sooner  or  later  adopt  the  same  system.  At  the  present  time  the  rail- 
roads, as  far  as  they  have  gone,  have  adopted  direct  current  because  the 
cities  through  which  they  pass  or  enter  are  using  direct  current.  When 
the  railroads  make  the  big  end  of  the  project,  however,  then  the  cities  will 
adopt  what  the  railroads  are  using.  When  this  comes  about  the  direct- 
current  railway  systems  in  the  cities  will  be  superseded  by  the  alternating. 

ME.  C.  V.  DEYSDALE  :  At  this  late  hour  in  the  discussion,  I  do  not  pro- 
pose to  take  up  your  time  very  much,  especially  as  I  am  afraid  that  very 
few  of  us  over  in  England  have  had  much  experience  on  this  important 
subject.  I  should  like,  in  the  first  place,  to  take  this  opportunity  of  con- 
gratulating you  on  this  side  of  the  water  on  having  carried  this  important 
problem  to  such  an  extremely  successful  issue  as  has  been  recently  shown  in 
Ballston  and  in  other  places.  I  think  this  subject  has  been  worked  on  in 
several  places,  yet  to  America  belongs  the  honor  of  having  constructed  the 
first  line  of  any  considerable  length  working  on  the  single-phase  system.  We 
must  still  further  admire  the  way  in  which  it  has  been  done  when  we  re- 
member that  the  result  has  been  achieved  by  getting  over  the  great  diffi- 
culties that  stood  in  the  way  of  the  series  motor,  and  that  in  so  doing  it  has 
been  found  practicable  to  use  the  same  motive  plants  on  direct-  and  alter- 
nating-current lines.  That,  in  itself,  is  an  enormous  advantage  over  and 
above  that  of  being  able  to  use  the  single-phase  alternating  current. 

It  would  be  impossible  for  anyone  to  criticize  any  of  the  statements  that 
have  been  made  this  morning,  because  they  come  from  gentlemen  who  have 
had  such  exceedingly  minute  experience  in  the  special  branch  of  the  subject, 
that  their  remarks  must  be  taken  as  gospel,  at  any  rate  for  the  present. 

My  object  in  taking  part  in  the  discussion  is  rather  to  bring  the  matter 
back  to  first  principles.  This  subject  has  been  worked  upon  in  many  differ- 
ent ways,  and  although  the  laminated  series  motor,  which  seems  to  have  been 
the  first  to  give  us  results,  will  probably  explain  and  solve  the  problem,  yet 


AJiXOLD:     ELECTRIFICATION   OF  STEAM   RAILROADS.      107 

there  are  some  interesting  questions  as  to  whether  there  are  any  other  ways 
of  fulfilling  the  problem  which  may  have  other  advantages.  There  is  one 
thing  that  does  not  seem  always  to  be  kept  in  view  in  traction  matters,  in 
the  starting  of  the  cars,  and  that  is  the  very  simple  matter  that  in  the 
starting  of  the  car  you  do  not  require  power,  you  require  force;  if  you 
wish  to  get  anything  into  motion,  what  you  require  in  the  first  instance  is 
purely  force,  and  until  the  body  moves,  it  does  not  require  power  at  all. 
One  of  the  great  advantages  which  the  steam-engine  has  over  any  electrical 
system  up  to  the  present  time,  is  the  fact  that  when  you  first  turn  the 
steam  into  the  locomotive  you  get  the  pressure  on  the  back  of  the  cylinder 
and  get  the  starting  force  without  taking  any  power  from  the  steam.  If 
it  were  not  for  the  other  disadvantages  of  the  locomotive,  there  is  no  ques- 
tion that  that  one  point  would  give  it  a  strong  pull  over  anything  we  have 
electrical,  because  if  we  turn  to  the  ordinary  direct-current  motor,  we  find 
that  we  have  to  use  half,  or  with  one  motor,  the  whole,  of  the  full-load 
power  merely  to  secure  a  starting  torque.  This  has  several  objections.  Not 
only  is  this  uneconomical  and  wasteful  of  power,  but  it  throws  a  sudden 
strain  on  the  general  plant,  and  furthermore  has  to  be  wasted  in  resistances, 
and  these  resistances  sometimes  attain  a  considerable  magnitude.  With 
alternating-current  motors  these  matters  are  worse,  as  we  have  in  addition 
low  power-factors  and  consequently  difficulties  in  regulation. 

The  time  is  too  short  to  refer  to  many  other  systems,  but  I  will  mention 
one,  that  known  as  the  Ward-Leonard  system,  which  at  first  sight  appears 
to  be  an  unworkable  one.  In  the  Ward-Leonard  system,  as  I  understand 
it,  the  system  is  to  use  a  single-phase  motor  coupled  to  a  direct-current 
generator  which  runs  direct  current  on  the  locomotive  or  cars.  Of  course, 
the  indirectness  of  the  method  seems  to  put  it  at  fault,  but  on  the  continent 
that  method  has  been  developed  with  considerable  hope  of  success,  in  fact 
with  considerable  practical  success ;  and  it  has  this  great  advantage  that  by 
the  use  of  this  arrangement  you  can  start — get  your  starting  effort — with 
very  small  power  taken  from  your  station.  In  the  other  system — it  is  too 
well  known  for  me  to  describe  it  here — you  have  your  single-phase  motor 
continuously  running,  and  you  can  do  the  whole  of  the  regulation  of  your 
speed,  etc.,  by  merely  regulating  the  excitation  of  the  generator.  The  result 
is  that  it  is  possible  to  get  the  full  starting  effort  with  only  something  like 
one-third  or  one-quarter  of  the  full-load  current  on  the  motors.  That  is  so 
important  a  matter,  especially  in  view  of  the  huge  trains  liable  to  be  thrown 
on  the  plant  in  the  large  schemes  which  we  are  hoping  to  see  realized  in  the 
future,  that  I  think  we  should  give  that  method  the  consideration  which 
it  deserves,  although  it  at  first  sight  appears  to  be  roundabout.  In  addition 
to  that,  we  have  the  magnificent  system  invented  by  your  President,  Mr. 
Arnold,  and  I  hope  we  shall  hear  more  of  that  in  the  future.  My  only 
object  in  rising  was  to  ask  that  we  should  hear  as  much  aboul  these  systems 
as  possible. 

PRESIDENT  ABNOLD:  I  am  pleased  to  be  put  down  as  one  of  the  speakers 
on  this  subject,  but  Messrs.  Steinmetz  and  Lamme  have  so  thoroughly 
covered  the  subject,  and  Dr.  Drysdale  has  so  kindly  referred  to  the  other 
systems  known  to  most  of  you,  that  it  is  not  necessary  for  me  to  say  much 
more,  particularly  as  the  time  is  growing  short. 


108      ARNOLD:     ELECTRIFICATION  OF  STEAM   RAILROADS. 

I  will  correct  one  statement  by  Mr.  Lamme,  which  rather  puts  me  on  the 
defensive.  I  understood  him  to  state  that  his  announcement  of  the  single- 
phase  motor  made  in  September,  1902,  was  the  first  announcement  of  a 
single-phase  system.  I  beg  to  state  that  in  the  month  of  June  preceding, 
I  read  a  paper  on  a  single-phase  railway,  known  as  the  Lansing,  St.  Johns 
&  St.  Louis  Railway,  which  was  built  at  that  time  and  which  I  have  since 
put  in  operation.  I  do  not  think  it  is  just  for  the  statement  to  be  placed 
on  record  just  in  the  manner  in  which  it  was  made.  I  think  Mr.  Lamme 
meant  to  say  that  his  paper  was  the  first  formal  paper  on  the  subject,  but 
my  road  was  built  and  almost  ready  to  operate  at  the  time  that  he  made 
his  announcement. 

Now,  without  further  discussing  the  question,  I  am  going  to  call  upon  a 
gentleman  whose  name  is  known  to  all  of  you,  and  introducing  him,  I  am 
reminded  of  an  anecdote  about  a  little  negro  boy  who  sat  on  a  log  chopping 
away  with  a  hatchet.  A  man  coming  along  the  road  asked  him  how  old  he 
was  and  the  boy  answered :  "  If  you  goes  by  what  mother  says,  I'se  six, 
but  if  you  goes  by  de  fun  I'se  had,  I'se  'most  a  hundred."  If  you  judge 
the  man  who  is  to  address  you  by  his  looks,  he  is  a  young  man,  but  if 
you  judge  him  by  his  experience  he  is  "  most  a  hundred,"  and  is  the  father 
of  the  commercial  electric  railway.  I  have  pleasure  in  presenting  Lieut. 
Frank  J.  Sprague. 

MB.  F.  J.  SPRAGUE:  I  feel  quite  embarrased  by  this  pleasant  introduc- 
tion by  our  worthy  President  and  the  reception  which  you  kindly  give  me. 
The  subject  under  discussion  is  one  which  I  will  not  enter  into  at  any 
length  to-day,  for  I  see  by  the  hungry  and  thirsty  look  on  the  faces  of 
some  of  the  gentlemen  present  that  one  o'clock  is  near  at  hand,  and  that 
they  would  probably  rather  adjourn  for  luncheon  than  to  listen  to  any 
discussions  whatever. 

The  subject  on  the  card  is  how  best  to  use  the  alternating  current  in 
railway  motors.  It  is  largely  a  technical  question.  The  alternating-cur- 
rent motor  is  like  a  somewhat  brilliant  boy,  who  being  exposed  to  various 
diseases  has  contracted  a  number  of  them ;  he  has  had  a  moderate  experience 
in  mumps  and  measles,  and  a  touch  of  typhoid  fever,  and  the  various  doctors, 
many  able  ones  here  and  elsewhere,  have  administered,  sometimes  in  homeo- 
pathic but  oftentimes  in  allopathic  doses,  large  measures  of  quinine  and 
other  drugs.  Whether,  as  the  child  grows — and  we  are  all  hopeful  of  that 
child — and  he  is  subjected  to  the  various  climatic  conditions  of  commercial 
introduction  and  use,  those  undercurrents  of  disease  common  to  all  fevers 
will  recur,  or  whether  the  child  will  outlive  them  and  become  strong  and 
robust  is  a  matter  which  must  be  left  to  future  developments. 

There  is  a  larger  problem,  and  I  will  not  take  over  two  minutes  to  speak 
of  it.  It  is  perhaps  a  more  popular  one,  but  of  vital  interest  to  us  as 
engineers  who  are  called  upon  to  advise  managers  and  others  as  to  their 
financial  expenditures,  and  that  is :  will  electricity  be  used  on  trunk  lines  ? 
Our  worthy  President,  with  whom  I  have  the  honor  to  be  associated  on 
some  important  work  in  that  line,  is  very  hopeful,  and  so  am  I.  But  what 
are  the  reasons  which  may  dictate  the  adoption  of  electricity  on  trunk 
lines  ?  Will  it  be  because  an  economical  service  cannot  be  gotten  by  steam  ? 
No.  Will  it  be  because  there  cannot  be  obtained  to-day  an  efficient  service  ? 


ARNOLD:     ELECTRIFICATION   OF  STEAM  RAILROADS.       100 

Again,  no.  Will  it  be  because  of  aesthetic  reasons?  Distinctly  not.  If 
electricity  be  adopted  on  any  trunk  line  service  it  will  be  because  of  the 
hard  and  fast  rule  of  financial  necessity,  not  because  we  engineers  urge  it. 
It  will  be  because  the  men  who  raise  the  money,  run  the  road  and  have  to 
provide  dividends  find  that  it  is  the  best  way  to  do  it,  and  the  reasons 
which  will  apply  to  one  road  are  not  necessarily  those  which  will  apply 
to  another.  It  is  my  belief  that  some  of  the  largest  expenditures,  and 
those  most  fruitful  of  return  to  those  who  own  the  steam  railroads  of  the 
country  to-day  will  be  for  the  purchase  and  control  of  competing  electric 
railways  which,  having  in  the  past  acquired  franchises  of  undoubted  value 
which  cannot  be  duplicated,  have  built  up  a  profitable  business  which 
they  can  hold  and  which  will  increase.  Many  a  steam  railroad  will  be 
better  off  financially  and  get  bigger  returns  if  it  gathers  in  these  franchises 
and  systems,  and  operates  its  whole  property  with  proper  regard  to  the 
needs  and  capacities  of  each  division  than  by  electrification  of  its  main 
lines,  at  least  for  a  long  time  to  come.  I  know  there  are  one  or  two 
gentlemen  back  of  me  who  feared  that  I  would  make  some  break  on  the 
subject,  so  I  will  close  my  remarks.  I  thank  you  for  your  kind  attention. 

PRESIDENT  ARNOLD:  We  now  desire  to  hear  from  a  gentleman  whose 
early  work  is  known  in  many  fields,  especially  in  the  electric  lighting  field. 
His  name  was  carried  by  one  of  the  leading  electrical  manufacturing  com- 
panies for  many  years  and  it  stands  to-day  on  much  of  the  material  that 
was  manufactured  in  the  early  days.  He  is  a  man  who  has  done  much 
research  work,  and  also  considerable  experimental  work  on  the  repulsion 
motor,  a  gentleman  whom  you  all  know  and  whom  you  recently  honored  by 
electing  him  President  of  the  International  Electrical  Congress.  I  have 
much  pleasure  in  introducing  Professor  Elihu  Thomson. 

PRESIDENT  ELIHU  THOMSON:  It  is  certainly  a  pleasure  to  me  to  listen  to 
a  discussion  of  this  kind  in  a  joint  meeting  of  the  Institution  of  Electrical 
Engineers  of  Great  Britain,  the  American  Institute  of  Electrical  Engineers, 
and  a  Section  of  the  International  Electrical  Congress.  It  is  gratifying  to 
find  that  there  is  so  little  dissent  from  the  statements  which  have  been  made 
as  to  the  future  of  alternating-current  traction.  Many  of  you  will  recall, 
no  doubt,  that  at  one  time  the  electrical  profession  might  have  been  said 
to  have  been  divided  into  two  camps,  the  alternating-current  camp 
and  the  direct-current  camp.  The  gentleman  who  preceded  me  was 
probably  at  that  time  more  to  be  found  in  the  direct-current  camp  than 
any  other.  The  other  gentlemen  who  have  preceded  me  were  to  be  found  in 
the  alternating-current  camp.  It  is  a  fact,  however,  and  those  who  have 
visited  the  power  stations  on  the  circular  tour  have  noticed,  that  the  direct- 
current  men  have  called  in  the  alternating  current  to  help  them  out,  and 
combine,  therefore,  the  virtues  of  the  alternating  current  with  the  virtues 
of  the  direct  current. 

I  was  connected  in  the  early  days,  and  am  still  connected,  with  an 
organization  which  had  not  many  prejudices  of  one  kind  or  another.  We 
had  direct  current,  we  had  constant  current  series  arc  lights,  constant- 
potential  direct-current  systems,  and  when  the  alternating  current  came 
we  were  ready  to  take  that  up  without  prejudice,  and  find  out  what  there 
was  in  it. 


110      ARNOLD:     ELECTRIFICATION   OF  STEAM   RAILROADS. 

In  1886  we  put  out  our  original  alternating-current  apparatus,  and  find- 
ing that  the  necessity  might  perhaps  arise  for  motors  on  the  system, 
it  was  at  that  time  I  undertook  to  get  a  motor  for  that  system,  a 
self-starting  alternating-current  motor,  and  the  first  motor  of  the  repulsion 
type  was  made  in  1886  and  finished  in  the  fall  of  that  year.  It  was  a 
little  affair  and  was  found  not  to  operate  very  well  on  the  higher  fre- 
quencies, but  by  connecting  it  to  a  machine,  which  1  was  using  for  electric 
welding,  giving  30  cycles,  I  found  it  operated  very  well  and  satisfied  me 
as  to  the  general  features  of  the  machine.  That  machine,  unfortunately, 
was  sent  to  an  exposition  and  lost — I  could  never  trace  it,  and  it  never  came 
back.  The  Paris  Exposition  of  1889  had  a  couple  of  examples  of  machines 
on  a  little  different  basis.  One  of  them,  I  believe,  is  in  England,  at  the 
Royal  Institution,  and  another  we  have  at  Lynn.  It  was  a  machine  which 
was  started  as  a  series  alternating-current  motor,  and  as  soon  as  it  reached 
a  certain  speed  the  commutator  was  short-circuited  and  it  became  an  induc- 
tion motor.  It  combined,  therefore,  the  elements  of  both,  but  1  will  admit 
that  the  design  of  such  machines  in  those  days  was  poor.  We  did  not  have 
even  the  distributed  winding;  we  did  not  have  the  arrangements  and  the 
proportioning  which  we  have  to-day ;  nevertheless  those  little  motors  would 
give  a  half-horse  power  for  a  moderate-sized  motor  on  125  cycles,  which 
was  the  highest  frequency  used.  1  merely  mention  these  items  as  matters 
of  history  touching  on  the  discussion.  They  have  nothing  to  do  with  the 
discussion  as  to  the  different  methods  and  systems  of  using  alternating 
current  in  electric  railway  motors,  but  I  am  a  strong  believer  in  the  field 
being  open  for  such  work.  I  believe  that  not  only  will  the  direct-current 
motor  maintain  its  place,  but  that  certain  lines  of  service  which  the  direct- 
current  motor  cannot  easily  take  will  undoubtedly  be  taken  by  the  alternat- 
ing-current motor  for  railway  service,  and  the  exhibition  of  a  system,  which 
you  have  been  able  to  see  in  use,  and  which  adapts  itself  to  the  use  of 
both  currents,  is  certainly  a  very  instructive  one. 

PBESIDENT  ARNOLD:  It  occurs  to  me  that  I  may  not  have  put  my 
explanation  in  regard  to  Mr.  Lamme's  statement  in  just  the  way  it  should 
be  put.  I  think  what  he  meant  was  that  his  announcement  was  the  first 
of  a  purely  single-phase  commutator  motor  system.  I  think  with  this  cor- 
rection he  will  accept  my  statement.  He  has  not  sent  me  any  word,  but 
this  additional  statement  is  due  him.  I  think  my  work  was  first,  but  he 
got  in  with  his  announcement  in  September  regarding  the  single-phase 
commutator  motor. 


ALTERNATING     vs.     DIRECT-CURRENT 
TRACTION.* 


BY  PROF.  DR.  F.  NIETHAMMER. 


Even  if  one  considers  only  serious  proposals,  there  will  be  found 
available  quite  a  considerable  number  of  electric  railway  systems 
which  might  be  used.  None  of  the  known  systems  possess,  how- 
ever, advantages  or  features  of  such  a  kind  as  to  render  it  able  to 
replace  all  others.  This  fact  becomes  specially  conspicuous,  if  an 
electric  railway  is  desired  which  is  adapted  equally  well  to  all  the 
various  services  occurring  in  railway  practice,  viz.,  short  and  long 
lines,  high  and  low  speeds,  short  and  long  distances  between  sta- 
tions, heavy  and  light  traffic. 

At  the  present  time  the  following  electric  systems  may  be 
considered : 

•  1.  DIRECT-CURRENT  RAILWAYS. 

a.  Two-wire  systems. —  Constant  pressure  from  500  to  1000  volts 
on  the  train,  the  return  circuit  being  the  rails.  Motors  with  large 
inputs  and  moderate  speeds  may,  however,  safely  be  built  for  pres- 
sures up  to  2000  volts,  by  using  double  commutators  if  necessary, 
or  by  grouping  several  motors  in  series. 
ml 


FIG.  1. —  THREE-  WIRE  DISTRIBUTION  SYSTEM  (KEIZIK,  PBAG). 
b.  Three-wire  systems. —  Constant  pressure  up  to  2X1200=2400 
volts  (Line  built  by  Thury,  Geneva;  City  &  South  London  Eail- 

*  As  I  did  not  think  it  advisable  to  change  the  paper  as  it  originally 
ran,  I  add  an  appendix  containing  the  most  recent  progress.  The  author 
treats  the  above  subject  in  a  much  more  complete  way  in  a  German  book 
"  Die  elektrischen  Bahnsysteme  der  Gegenwart."  As  to  single-phase  rail- 
way motors  see  also  Electrical  Magazine,  October  and  November,  1904. 

run 


112  NIETHAMMER:     ELECTRIC    TRACTION. 

way  with  4X500  volts).  2X2000  volts  seem  to  be  a  safe  limit  for 
this  system.  Each  train  may  either  be  fed  by  one  branch  of  the 
three-wire  net-work,  in  which  case  the  pressure  per  train  is  half  of 
the  whole  voltage,  and  only  one  trolley  is  necessary;  or  each  train 
may  take  the  whole  voltage  by  two  trolleys  the  connection  of  two 
motor  groups  being  grounded  and  the  rails  being  the  neutral 
conductor.  (Fig.  1.) 

By  installing  boosters  or  direct-current  transformers  in  the  cen- 
tral station  or  along  the  line,  the  distance  which  may  be  covered 
by  the  simple  direct-current  system  may  be  somewhat  enlarged; 
the  same  result  may  be  arrived  at  by  using  storage  batteries  at 
some  feeding  points  of  the  line. 

c.  Direct-current  railways  with  transmission  by  three-phase  cur- 
rents.—  The  direct-current  pressures  on  the  trains  remain  the  same 
as  under  (a)  and  (&) ;  the  three-phase  voltages  go  as  high  as 
60,000,  transformation  being  by  rotaries  or  motor  generators.  The 
transmission  may  also  be  effected  by  the  direct-current  system  with 
constant  current  and  variable  voltage  up  to  30,000  volts  (Thury). 

In  all  the  cases  mentioned,  the  simple  series  motor  is  almost  ex- 
clusively used,  with  the  exception  of  mountain  railways  with  low 
constant  speed.  For  the  latter  case  the  shunt  motor  is  preferable, 
as  this  type  is  able  to  return  energy  to  the  line. 

2.  THREE-PHASE  EAILWAYS. 

Induction  motors  on  the  train.  Safe  trolley  wire  voltages  are 
500  to  3000  (5000)  volts,  the  pressure  of  10,000  volts  of  the 
Berlin-Zossen  high  speed  line  being  only  experimental.  The  trans- 
mission may  use  pressures  up  to  60,000  volts  which  are  reduced  by 
stationary  transformers  preferably  of  the  oil  type. —  Of  some  inter- 
est for  three-phase  lines  is  the  compensated  polyphase  induction 
motor  with  commutator,  which  has  been  proposed  for  this  work. 

3.  SINGLE-PHASE  COMMUTATOR  MOTORS. 

The  highest  trolley  wire  voltage  advisable  at  present  is  about 
6000  volts,  though  the  Maschinenfabrik  Oerlikon  proposes  and  is 
using  15,000  volts  on  an  experimental  line,  which  involves  less  risk 
for  a  system  with  one  trolley  wire  than  for  a  system  with  two  or 
three.  There  are  available  for  traction  three  types  of  single-phase 
motors:  The  series  motor  (Westinghouse  Company,  General 
Electric  Company),  the  repulsion  motor  (Brown,  Boveri  &  Cie) 


NIETHAMMER:     ELECTRIC    TRACTION.  113 

and  the  compensated  or  series-repulsion  type   (Winter-Eichberg, 

Union  E.  G.). 

•    The  following  systems  are  of  sufficient  practical  interest  to  be 

mentioned,  but  they  cannot  be  considered  serious  competitors  to  the 

foregoing. 

4.  CURRENT  CHANGERS. 

Converters  or  electric  generators  on  the  train. 

a.  Ward-Leonard  system  and  shunting  locomotive  of  the  Mas- 
chinenfabrik  Oerlikon.     The  train  takes  single-phase  current  at 
high  voltage  from  the  trolley  line  and  transforms  it  into  direct 
current  by  a  high-speed  motor-generator  set.     By  changing  the 
small  exciting  current  of  the  direct-current  generator,  speed  con- 
trol of  the  train  may  be  accomplished,  and  during  retardation 
energy  may  be  returned  to  the  line.     The  main  drawback  of  this 
excellent  system  is  the  excessive  weight  and  price  of  the  motor 
generator,  which  weighs  more  than  all  car  motors  together. 

b.  Combination  of  steam  engines,  steam  turbines  or  oil  (petro- 
leum)  engines  with  direct-connected  direct-current  generators. — 
Regulating  is  done  as  in  case  a.    Of  this  type  is  the  old  Heilmann 
locomotive  and  a  new  car  of  the  North  Eastern  Eailway  in  Eng- 
land, which  latter  contains  a  horizontal  oil  engine  directly  con- 
nected to  a  compound  generator  of  55  kilowatts  300  to  550  volte 
and  420  to  480  revolutions  per  minute. 

5.  SINGLE-PHASE  INDUCTION  MOTORS. 

First  proposed  by  C.  E.  L.  Brown  but  having  little  chances  of 
being  applied  practically. 

a.  Stator  and  rotor  both  revolve;  the  stator  is  brought  up  to 
speed  without  load.    By  gradually  retarding  the  stator  by  means 
of  a  brake,  the  rotor  which  is  connected  to  the  car  wheels  is  put 
in  motion. 

b.  The  induction  motor  is  started  empty  and  connected  to  the 
car  wheel  through  a  flexible  friction  clutch. 

c.  Stator  and  rotor  are  connected  with  a  device  capable  of  stor- 
ing up  energy,  which  device  absorbs  or  delivers  energy  at  will, 
i.  e.,  an  air  compressor  (B.  J.  Arnold)  or  oil  pumps  with  variable 
stroke  (Swinburne)  or  water  pumps  (Siemens  &  Halske).     This 
system  possesses  the  advantage  of  ability  to  operate  for  short  dis- 
tances without  connection  to  the  electric  supply  circuits. 

ELEC.    BYS. —  8. 


114  NIETHAMMER:    ELECTRIC  TRACTION. 

6.  CONSTANT  DIRECT-CURRENT  SYSTEM. 

Various  trains  are  switched  in  series  by  a  double  trolley  wire 
system.  The  total  voltage  is  variable,  and  it  is  proposed  to  go  as 
high  as  30,000  volts.  The  constant-current  system  is,  however,  too 
complicated  and  unreliable  for  distributing  purposes,  though  it  is 
excellent  for  transmission  lines.  Speed  variation  and  starting  would 
be  very  economical  and  returning  energy  to  the  line  very  simple. 
The  continuous  losses  in  the  line  would,  however,  be  considerable. 

7.  MOTOR  CARS  WITH  STORAGE  BATTERIES. 

Independent  of  every  outside  source  of  current  and  always  ready 
for  service.  Such  locomotives  are  heavy1  and  expensive  and  serve 
only  for  factory  or  shunting  purposes  or  for  short  lines  with  light 
and  constant  traffic  and  with  low  acceleration.  The  mixed  service 
using  partly  storage  batteries  and  partly  overhead  line  has  entirely 
failed.  There  were  also  proposed  railway  plants  combining  storage 
batteries  with  single-phase  induction  motors.  Starting  is  done 
b)  the  battery,  free  running  and  charging  by  the  transformed  single- 
phase  current. 

The  above-mentioned  systems  should  be  compared  with  regard  to 
first  cost,  operating  expenses,  reliability  and  safety  in  service.  This 
comparison  is  to  be  made  for  lines  of  few  kilometers  in  length 
(street  railways)  and  for  hundreds  and  thousands  of  kilometers 
(main  lines),  for  speeds  of  10  km  per  hour  up  to  100  and  150  Ion; 
for  accelerations  of  0.1  m  per  sec.2  to  more  than  1  m  per  sec.2, 
the  retardation  being  even  higher  by  20  to  40  per  cent.  The 
train  weights  vary  from  5  tons  to  about  2000,  and  the  number  of 
horse-power  per  train  from  10  to  4000.  There  are  lines  with  only 
10  trains  a  day,  on  others  the  trains  follow  at  intervals  of  3  min- 
utes. In  one  case  the  stations  are  separated  by  a  distance  of  only 
200  meters,  on  others  more  than  100  km.  In  the  first  case  the 
whole  service  is  starting,  coasting  and  braking;  in  the  other  case 
free  running  is  of  most  importance.  Either  motor  cars  with  mul- 
tiple unit  control  for  motors  distributed  over  the  whole  train  or  lo- 
comotives may  be  used.  Electric  traction  is  specially  qualified  for 
motor  car  service  of  passenger  as  well  as  of  freight  trains  which 
service  requires  frequent  short  trains  of  variable  length.  Electric 

1.  A  storage  battery  locomotive  for  a  whole  train  weight  of  100  tons  for 
16  km  an  hour  weighs  26.8  tons;  the  storage  battery  absorbs  10  tons  and 
the  remaining  electric  equipment  4.3  tons. 


NIETHAUUER:     ELECTRIC    TRACTION.  115 

motors  are  also  able  to  haul  heavier  trains  than  steam  engines  and 
to  exceed  the  latter  in  speed.  (Baltimore-Ohio  1600  tons  trains. 
New  York  Central  trains  of  2X2200  horse-power,  max.  2X2800 
horse-power.)  Single  motor  cars  take  more  watts  per  ton-km  than 
long  trains.  A  very  hard  problem  is  offered  by  motor  cars  which 
must  be  used  for  short  and  long  distances  between  stations,  for  low 
and  high  speeds,  and  for  short  and  long  lines  and  for  light  and 
heavy  service  at  the  same  time.  For  this  service,  however,  elec- 
tricy  is  better  adapted  than  steam. 

The  main  data  for  usual  railway  traffic  may  be  taken  from  the 
following  table,  which  gives  the  limiting  values  corresponding  to 
light  and  heavy  traffic: 


116 


NIETHAMMER:     ELECTRIC    TRACTION. 


I 


1 

| 

CO 

CM 

M 

8 

S 

o 

S2S 

,0 

jl 

.2t 

i! 

o 

3 

3 

«a 

d 

3 

CM 

3 

3 

3 

0 

333 

coccus 

S 

o 

c 

5 

2 

J^ 

eo 

-a 

0 

t- 

CM 

CO 

to 

a 

— 

*3 

i 

d 

a 

T-l 

O 

0 

o 

0 

3 

2 

1 

3 

oa 

3 

3 

3 

3 

3 

w-  - 

1 

J2 

P« 

,_| 

•^4 

en 

10 

,H 

(N 

>, 

>» 

8 

^ 

O 

O 

o 

d 

0 

0 

1 

® 

<j 

a 

*, 

j 

1 

§ 

? 

1 

§S 

§o 
25 

IS 

111 

8 

Ir 

S 

3 

IO 

3 

3 

3 

o'il 

^O^g 

5§1 

S 

"S 

fl" 

S 

8 

8 

43  o  ° 

3  o  ° 

80° 

y 

* 

1 

Sjf 

s_ 

Ms' 

- 

3 

CO 

10 

10 

^ 

^ 

1^ 

CM 

O  < 

i> 

Is 

-4     O 

3 

o 

3 

3 

§ 

I 

o 

1s  s 

3 

g 

f  0 

i 

« 

§S 

3 

CO 

•s, 

1 

3«5 

s  o 

** 

1H 

CO 

3 

CO 

3 

CM 

3 

1 

I 

I^THtH 

iH 

I 

53 

1 

§ 

fc 

»" 

•3 

8 

1 

1 

1 

§ 

1 

§ 

§11 

1 

3 

3 

o 

3 

3 

3 

CO 

3 

3 

eo 

3 

3 

&H 
H 

8 

S 

8 

1 

V 

8 

S 

? 

1 

1 

8 

§ 

9g| 

S 

Motors 

SI 

1 

3 

o 

3 

3 

3 
8 

3 

3 

3 
8 

3 

1 

CM 

3 

l-H 

3 

00 

3 

00 

3 

CM 

CO 

3 

i 

2 

^"^ 

CM 

3 

rl 

a 

•o 

"^ 

s 

1 

fl 

55 

03 

M 

* 

8 

8 

8 

a 

§ 

g 

s 

883 

0 

& 

£§ 

3 

o 

3 

00 

3 

3 

3 

o 

3 

3 

3 

IO 

I" 

P 

8 

g 

4 

1 

i 

s 

1 

Street  railways,  with  radial 
lengths  of  1  to  30  km  trorr  cen  er 
and  gauges  of  600  to  1  .43<  mm  .  . 

Industrial  and  mine  locon  olives, 
gauge  800  to  1,436  mm  

Elevated  and  underground,  10  to 
40  km  length,  multiple  unit  

Suburban  and  interurban  ser- 
vice, 10  to  200km  radial  length, 
multiple  unit  

oa 
1 

I 

I 

V-           .—i 

1 

1 

II  passenger  trains, 
locomotives  x 

1 

(Steep)  Gothard  line,  26*  grade 
freight  

express  

|  Mountain  Ry  

-NIETHAMMER:     ELECTRIC    TRACTION. 


117 


II 


Jfl 

Id 


1 

fc 

c 

I— i 
EH 
Q 


i 


K 


1      1 

X     V 


sg 


S    8 


•§s 

So 

II 


^S 

r 


irect  curr 
Baltimore 

New  York 


MS  NIETHAMMER:     ELECTRIC    TRACTION. 

The  energy  input,  the  watts  per  ton-kin  grow  with  increasing 
speed,  i.  e.,  an  increase  from  32  to  128  km  per  hour  means  an  in- 
crease of  input  of  45  per  cent  per  ton-km.  High  acceleration  cer- 
tainly ^requires  lowest  total  watt  consumption  for  starting,  but  it 
causes  excessively  high  starting  currents,  necessitating  large  and 
expensive  motors  and  drawing  excessive  loads  from  the  central  sta- 
tion. For  short  distances  between  stations  it  is  most  economical 
to  run  very  fast  up  to  a  high  speed,  if  admissible,  and  to  coast  as 
long  as  possible  without  current.  The  maximum  acceleration  de- 
pends upon  the  allowable  shock  to  passengers  when  starting;  much 
more  than  1  m  (per  sec.)2  will  not  be  permissible.  The  best  method 
is  to  increase  acceleration  gradually  when  starting  and  to  let  it  die 
out  finally  without  any  shock. 

Undoubtedly  a  reasonable  electric  railway  service  can  be  offered 
in  economical  competition  with  steam.  On  the  Italian  line  from 
Milan  to  Porto  'Cerisio  (130  km  direct  length,  70-ton  trains,  accel- 
eration 0.35  m  (per  sec.)2  and  speed  of  90  km),  the  introduction 
of  electric  service  has  increased  the  number  of  travellers  2£  times, 
the  train-km  4  times  and  the  trains  per  day  have  grown  to  120 
from  about  20  during  steam  service.  The  receipts  and  profits  ob- 
tained render  this  line  the  most  economical  in  all  Italy,  though 
steam  is  used  for  generating  electricity.  Most  favorable  to  elec- 
tric traction  are  most  urban  and  suburban  lines,  railways  with  dense 
traffic  or  those  so  located  that  the  traffic  could  not  be  increased 
without  an  additional  line,  railway  tracks  with  long  tunnels  and 
heavy  grades  and  lines  which  are  in  the  neighborhood  of  coal  mines 
and  water  powers. 

A  comparison  of  the  various  electric  systems  should  comprise 
the  whole  electric  equipment,  viz.:  a.  Motors  and  gearing; 
&.  regulating  and  braking  devices;  c.  current-collecting  devices; 
d.  central  stations  and  sub-station  equipments. 

MOTORS. 

The  characteristic  features  of  railway  motors  are, 
1..  Mechanical  reliability. 

2.  Maximum  pressure  possible  on  motor  terminals  and  maxi- 
mum pressure  at  the  trolley. 

3.  Sparking  on  commutator  or  collector. 

4.  Weight  per  horse-power  at  a  definite  speed. 

5.  Space  occupied  by  motor. 


JflETHAMMER:     ELECTRIC    TRACTION.  119 

With  heavy  train  loads,  high  speeds  and  great  accelerations  it  is 
often  extremely  difficult  to  make  sufficient  space  available  on  the  car 
truck  for  the  large  motors  required.  The  room  available  increases 
with  increasing  diameter  of  the  wheels  and  with  broader  gauges. 
It  is  a  fact,  that  on  a  300-mm  gauge  only  15-hp  motors  are 
possible,  on  a  700-mm  gauge  only  90  horse-power,  on  1000-mm 
gauge  about  150  horse-power  and  on  normal  gauge  250  horse-power. 

6.  Efficiency  at  full  and  partial  loads. 

7.  Starting  losses  of  the  motor. 

8.  Power  factor  at  full  load,  partial  loads  and  at  starting. 

9.  Heating  for  normal  continuous  running  and  for  frequent 
starting. 

10.  Starting  torque  and  possibility  of  produciag  high  accelera- 
tion; current  consumption  for  a  definite  starting  torque. 

11.  Efficiency  of  acceleration. 

12.  Speed  variation;  losses  and  efficiencies  at  variable  speeds. 
Steadiness  of  regulation.     Speed  characteristic  for  variable  loads. 

13.  Braking  on  resistances  and  return  of  power  into  the  line, 
when  coasting  or  on  grades. 

The  direct-current  series  motor  has  an  air-gap  of  2.5  to  7  mm  for 
usual  armature  diameters  of  300  to  600  mm,  the  upper  gap  being 
smaller  by  J  to  1  mm  than  the  lower.  Experience  on  hundreds  of 
thousands  of  such  motors  prove  that  this  air-gap  is  absolutely  safe 
and  that  there  is  no  danger  of  sticking.  The  direct-current  arma- 
ture winding,  with  open  slots  and  carefully  wound  separate  coils, 
as  well  as  the  commutator,  may  be  insulated  in  .in  absolutely  reli- 
able way  for  voltages  up  to  2000.  The  field  winding  has  no  high 
potential  between  its  terminals  and  is  easily  protected  against  the 
frame,  whilst  the  field  winding  of  shunt  motors,  being  subject  to 
full  pressure,  is  much  more  liable  to  break  down. 

The  induction  motor,  if  only  that  type  without  commutator  is 
considered,  must  have  an  air-gap  from  1  to  3  mm  in  depth  for  usual 
railway  motors,  according  to  size,  in  order  to  secure  a  satisfactory 
power  factor  and  a  sufficient  overload  capacity.  The  Valtellina 
motors  with  a  rotor  diameter  of  800  mm  have  an  air-gap  of  2  mm. 
Values  for  other  machines  may  be  taken  from  Table  II.  According 
to  the  long  practical  experiences  of  Brown,  Boveri  &  Cie.,  and  of 
Ganz  &  Company,  this  small  air-gap  has  never  given  rise  to  trouble, 
when  the  bearings  are  liberally  designed.  C.  E.  L.  Brown  has  suc- 
cessfully used  automatic  ring  lubrification  for  three-phase  motors. 
Nearly  closed  slots  should  preferably  be  used  to  get  smooth  cylin- 


120  NIETHAMMER:     ELECTRIC    TRACTION. 

drical  surfaces  along  the  air-gap,  which  makes  it  a  necessity  to 
wind  the  coils  by  hand.  This  type  of  winding  with  closed  mica 
tubes  in  the  slots  and  end  connections  well  protected  by  bronze  caps 
has  never  caused  trouble  on  the  Burgdorf-Thun  or  the  Valtellina 
line.  Special  care  must  be  given  to  the  crossings  of  the  end  con- 
nections, but  insulation  may  be  obtained  to  withstand  easily  pres- 
sures up  to  5000  volts.  High  voltage  motors  must,  however,  be  very 
Liberally  dimensioned  to  keep  down  heating  which  deteriorates  in- 
sulation. It  may  be  of  advantage  to  put  the  stators  of  two  three- 
phase  motors  in  series  to  reduce  the  voltage  per  motor  (Fig.  2). 
The  air-gap  of  the  single-phase  commutator  motor  must  also 
be  rather  small,  though  larger  than  with  the  three-phase  motor, 
i.  e.,  3  mm  for  a  rotor  diameter  of  450  mm.  Commutator  motors, 
the  rotors  of  which  are  not  fed  directly  from  the  line,  are  the  best 
machines  for  high  voltages  up  to  8000  volts,  as  all  crossings  of 
the  end-connections  can  be  easily  avoided.  For  equal  line  voltage 


tin. 

IM— j— i 

UI-JT      |-"S*f 


*** 

n 

Fw.  2. — STATORS  IN  SEBIES. 

the  single-phase  motor  in  comparison  with  the  direct-current  motor 
is  at  a  disadvantage  in  that  there  is  an  active  e.m.f.  across  not  only 
the  armature  but  also  the  field  coils. 

The  trolley  voltage  of  all  alternating  current  equipments  of  the 
single  or  polyphase  type  may  be  lowered  at  will  by  transformers  on 
the  car,  if  on  account  of  limited  space  or  due  to  troubles  on  the 
commutator,  one  is  bound  to  use  low  voltage  motors.  That  means, 
however,  additional  weight  and  expense,  though  the  transformers 
may  be  used  for  regulating  purposes  at  the  same  time. 

The  frame  of  single  or  polyphase  motors  can  hardly  be  split,  as 
is  frequently  done  with  direct-current  machines.  The  joints  might 
give  rise  to  noise.  As,  however,  even  for  direct-current  motors 
in  limited  space  the  splitting  of  the  frame  is  being  abandoned  in 
favor  of  the  box  frame,  this  fact  is  not  of  much  importance.  From 
Fig.  3  which  represents  a  single-phase  commutator  motor  of  the 
Union  Company,  Berlin,  for  50  horse-power,  800  rev.  p.  min.,  40 


mETHAMMER:     ELECTRIC    TRACTION. 


121 


periods,  6  poles,  400  volts,  it  may,  however,  be  seen  that 
the  splitting  of  an  alternating  current  motor  is  not  an 
entire  impossibility.  Single-phase  winding  is  more  favor- 
able yet,  as  no  coils  have  to  be  cut.  The  laminated  field 
of  alternating-current  motors  is  less  rigid  than  that  of  the  direct- 
current  machine,  so  that  an  additional  solid  frame  becomes  neces- 
sary. For  direct-current  motors  which  must  undergo  rapid  varia- 
tions of  the  magnetic  flux  and  of  the  speed  or  which  must  be  quickly 
braked,  a  laminated  frame  would,  however,  also  be  of  advantage. 

The  greatest  drawback  of  direct-current  motors  is  the  difficulty 
of  commutation.  Sparking  in  the  neutral  zone  is  due  to  the  react- 
ance voltage  of  the  short-circuited  coils  and  to  the  voltage  induced 
by  the  distorted  main  field.  The  distortion  may  be  kept  low  by 
using  a  high  number  of  field  ampere  turns  and  high  saturations  of 


FlO.   3. —  50-HP   SINGLE-PHASE   MOTOR,   UNION  COMPANY. 

teeth  and  pole  shoes.  The  reactance  is  small  for  low  speed  motors, 
for  short  armatures,  for  small  currents  per  armature  circuit,  and  for 
commutators  with  many  segments.  Flashover  is  produced  by  high 
voltages  per  segment  and  by  current  rushes,  when  at  high  speeds 
the  current  circuit  is  suddenly  opened  and  closed  again.  These  are 
the  reasons  why  direct-current  motors  have  not  been  built  as  yet  for 
more  than  1000  volts,  though  larger  low-speed  types  may  success- 
fully be  designed  for  about  2000  volts.  To  raise  the  trolley  voltage, 
several  motors  may  be  switched  in  series,  but  this  scheme  has  the 
drawback  that  when  some  wheels  with  motors  are  slipping  and  others 
not,  one  or  several  motors  may  get  the  full  voltage  at  their  terminals 
and  be  burned  out.  The  series  motor  is,  of  course,  much  less  liable 
to  sparking  than  the  shunt  motor,  as  the  reactance  does  not  vary 
much  with  load  and  speed,  besides  that  armature  and  field  ampere- 


J22 


NIETHAMMER:     ELECTRIC    TRACTION. 


turns  increase  together.  This  commutation  trouble  is  the  most 
serious  handicap  to  the  direct-current  motor,  as  it  limits  the  exten- 
sion of  its  supply  lines. 

The  three-phase  motor  has  no  commutation  problems.    The  space 
for  the  three  slip  rings  with  carbon  brushes  is,  however,  not  smaller 


\L> 


if—  short  circuit  current 
T«  time  for  commutation. 


FIGS.  4  AND  5.  —  COMMUTATION  CHABACTERISTICS. 

than  that  for  a  commutator.  Even  the  commutator  for  compensated 
polyphase  motors  is  easily  designed,  as  it  is  a  mere  frequency  changer 
with  low  voltage.  With  regard  to  sparking,  single-phase  commu- 
tator motors  offer  the  greatest  difficulties.  First  of  all,  an  alternat- 
ing -current  has  to  be  commutated,  a  process  which  changes  every 
moment  (Figs.  4  to  6).  Sparking  is  due  not  only  to  the  reactance 
voltage  (er)  and  the  voltage  («a)  induced  by  the  main  field  during 


FIG.  6  —  COMMUTATION  CHAKACTERISTICS. 

rotation,  but  to  a  transformer  voltage  ei  which  is  induced  by  the 
oscillations  of  the  main  field  independent  of  speed  and  which  pro- 
duces a  high  short-circuit  energy.  By  using  low  commutator  volt- 
ages (smaller  than  200  volts),  a  high  number  of  commutator  bare 
preferably  with  multiple  parallel  winding,  by  selecting  thin  brushes 


NIETBAMMER:     ELECTRIC   TRACTION. 


12;] 


(minimum  6  to  10  mm),  by  inserting  high  resistances  into  the  short- 
circuited  coils,  by  reducing  the  main  field  and  by  building  only 
motors  for  small  outputs  and  small  periodicities,  the  transformer 
voltage,  el,,  may  be  kept  sufficiently  low.  The  reactance  voltage,  ^ 
is  cut  down  by  the  same  expedients  as  used  for  direct-current 
motors.  Equalizers  and  auxiliary  commutation  poles  may  be  of  ad- 
vantage, but  there  will  rarely  be  space  available  for  them.  By  a 
double  (horseshoe)  pole  excited  by  the  main  current  opposite  to  the 
short-circuited  coil,  one  may  neutralize  the  whole  transformer 
effect.  The  General  Electric  Company  uses  a  distributed  field  wind- 
ing  to  neutralize  the  reactance  voltage  similar  to  the  Eyan  winding 
of  direct  current  machinery. 

The  repulsion  motor  and  the  compensated  motor  (Fig.  7)  have 
this  advantage  that  for  synchronism,  and  in  its  neighborhood,  a 
regular  rotating  field  is  built  up,  replacing  the  pulsating  alternating 
fields.  Near  synchronism  the  transformer  effect  in  the  coils  under 


Fio.  7. —  COMPENSATED  MOTOB.       PIG.  8. —  STARTING  COMMUTATOB  MOTOR. 


the  brush  is,  therefore,  eliminated  and  the  commutation  is  similar 
to  that  of  direct-current  machine.  Flashing  over  on  the  brushes 
of  a  repulsion  motor  seems  next  to  impossible  and  even  for  other 
commutator  motors  flashover  appears  less  probable,  as  self-induc- 
tion damps  away  sudden  current  rushes  and  the  laminated  stator 
frame  facilitates  the  rapid  building  up  of  magnetic  fields. 

When  starting,  all  commutator  motors  are  equally  bad  and  one 
of  the  best  schemes  besides  those  already  mentioned  is  to  use  a 
series  transformer  for  the  armature  circuit  (Fig.  8)  which  cuts 
down  the  starting  field,  allowing  at  the  same  time  any  intensity  of 
.  the  starting  current.  For  repulsion  motors,  the  same  effect  is 
possible  by  shifting  the  brushes  toward  the  position  of  complete 
transformer  action  (brush  axis  in  line  with  field  axis).  The  main 


124 


NIETUAMMER:     ELECTRIC    TRACTION. 


field  at  starting  may  also  be  prevented  from  rising  too  much  by 
choosing  the  iron  inductions  very  high. 

The  distortion  of  the  field  by  armature  reaction  and  the  wattless 
voltage  component  produced  by  it  may  easily  be  neutralized  for  the 
single-phase  series  motor  by  a  field  winding,  the  axis  of  which  coin- 
cides with  the  armature  cross-field  and  which  may  be  short-circuited 
or  in  series  with  the  armature  current  circuit.  Figs.  9  and  10  show 
this  arrangement  as  used  by  Ganz  &  Company  15  years  ago.  Finzi 
splits  the  poles  for  the  same  purpose  and  cuts  down  the  polar  arc. 
Blathy  of  Ganz  &  Company  also  used  some  15  years  ago  high  tooth 
inductions2  and  ohmic  and  inductive  resistances  between  armature 
winding  and  commutator,  sometimes  imbedded  in  the  slots. 


FIG.  9. —  STATOB  PUNCHING. 

A  stator  with  definite  projecting  poles  has  the  advantage  of 
cutting  down  the  reactance  voltage  in  the  short-circuited  armature 
coils  and  gives  rise  to  smaller  armature  cross-field,  which  means 
a  better  power  factor  than  with  a  distributed  winding  imbedded  in 
slots  equally  spread  round  the  whole  circumference.  This  is  the 
reason  why  series  motors  should  always  have  definite  poles,  while 

2.  Lamme  proposes  high  pole-shoe  induction. 


NIETHAMMER:     ELECTRIC    TRACTION. 


125 


the  good  operation  of  repulsion  motors  depends  upon  the  full  devel- 
opment of  the  armature  cross-field  to  get  a  rotating  field  at  syn- 
chronism. Repulsion  motors  must,  therefore,  have  a  distributed 
winding.  The  better  leakage  factor  of  the  last-mentioned  winding 


FIG.  10. —  ROTOR  PUNCHING. 

is  outbalanced  by  the  better  voltage  factor  or  winding  efficiency  of 
a  concentrated  winding. 

Table  II  shows  weight,  outside  dimensions,  air-gap,  efficiency, 
etc.,  of  a  great  many  railway  motors  of  the  direct-current,  three- 
phase  and  single-phase  type,  most  of  which  are  in  actual  service : 


VIETHAMMER:     ELECTRIC    TRACTION. 


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NIETHAMMER:     ELECTRIC    TRACTION. 


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VIETHAMMER:     ELECTRIC    TIIAGT10M* 


NIETHAMMER:     ELECTRIC    TRACTION.  129 

For  equal  output,  speed  and  voltage  the  direct-current  motor  has 
usually  the  smallest  weight,  is  cheaper  and  takes  less  space  than 
all  its  rivals.  The  reasons  are:  That  the  field  is  solid  and  there 
are  no  lagging  currents,  the  concentrated  field  winding  is  very 
pimple  and  it  needs  no  inactive  frame,  the  inductions  in  all  iron 
parts  may  be  very  high,  in  the  teeth  up  to  27,000  lines  per  cm2,  in 
the  core  15,000  to  20,000,  in  pole  and  yoke  the  same,3  whilst  alter- 
nating-current motors  cannot  at  all  reach  these  values  on  account 
of  the  high  wattless  magnetizing  current.  Three-phase  motors  with 
variable  poles  or  concatenated  motors  have  even  higher  weights. 
The  commutator  of  single-phase  motors  must  be  larger  than  that 
for  direct-current  machines  on  account  of  the  much  higher  commu- 
tator losses  and  because  the  voltage  must  be  kept  very  low  (less 
than  200  volts).  If  both  a  single-phase  and  a  direct-current  motor 
are  laid  out  for  the  same  maximum  field  flux  ^^^  and  the  same 
effective  current  I,  the  normal  torque  TA  of  the  alternating-current 
motor  becomes 

TA  =  -L  C*  #max  - 1  •  ^  •  8in?  a  d  a  _  0.71  Q^  •  I 

It    J  o 

and  that  of  the  direct-current  type  TA 

J- d  ==  *max  •  •* 

That  means  for  the  same  torque  and  output  the  single-phase  motor 
must  be  30  per  cent  larger.  For  placing  a  motor  into  the  car  truck, 
a  cylindrical  body  (alternating-current  motors)  is  less  practical 
than  a  prismatic  one  (direct-current).  As  on  varying  grades  and 
during  starting  the  three-phase  motor  absorbs  more  energy  than 
Dther  motors,  it  must  be  larger  and  more  expensive  for  this  reason 
also. 

The  efficiency  of  direct-current  motors  is  sometimes  somewhat 
-.mailer  than  that  of  three-phase  motors,  which  result  is  due  ex- 
clusively to  the  much  smaller  air-gap  with  the  latter  machine.  For 
the  same  air-gap  and  for  open  slots,  the  three-phase  motor  must 
have  a  lower  efficiency.  Single-phase  commutator  motors  have  a 
poorer  efficiency  than  direct-current  and  three-phase  motors;  with 
partial  loads  the  efficiency  is  especially  very  low.  The  losses  of  the 
single-phase  motor  usually  amount  to  15-35  per  cent  more  than 
those  of  the  direct-current  type.  The  increase  of  losses  is  due  to  ad- 

3.  The  current  densities  are  5  to  7  amps,  per  mm*  in  the  armature  and 
2  to  3  in  the  field,  in  three-phase  motor  4  to  5. 
ELEC.  BYS. —  9. 


130 


NIETHAMMER:     ELECTRIC    TRACTION. 


ditional  iron  losses  in  the  field  and  armature  at  standstill  and  when 
running,  and  furthermore/ to  the  energy  loss  in  the  coils  short- 
circuited  by  the  brushes.  For  the  straight  series  motor,  there  may 
be  additional  losses  in  resistances  of  the  commutator  connections 
and  in  auxiliary  windings.  The  repulsion  motor  has  the  advantage 
that  the  iron  losses  in  the  rotor  are  zero  for  synchronous  speed. 


BO 


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800  kg. 


600 


400j 


100 


50  HP.,  6  boles,  800  revs!,  900  volts.  40  fcertdds.  dear   atio  Lftffft 
whee'l  diameter  800  mm 


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PIG.  11. —  CHARACTERISTIC  CURVES  COMPENSATED  SERIES  MOTOR. 

Fig.  11  represents  all  characteristic  curves  of  the  compensated 
single-phase  motor  the  outline  of  which  is  given  in  Fig.  3.  Fig.  7 
shows  the  way  of  connecting  up  the  motor.  The  curves  marked 
1  to  5  correspond  to  a  variable  ratio  of  the  series  transformer. 


ELECTRIC    TRACTION.  131 

While  with  alternating-current  motors  the  number  of  poles  is 
fixed  by  the  synchronous  speed  or  for  the  series  motor  by  about 
double  synchronous  speed,  -and  by  periodicity,  which  is  usually 
kept  low  to  reduce  the  number  of  poles,  nearly  all  direct-current 
motors  have  four  poles,  rarely  six.  The  tendency  to  building  high- 
voltage  motors  makes  the  use  of  only  two  poles  advisable.  This 
scheme,  which  is  used  by  the  General  Electric  Company  for  the 
550-horse-power  motors  of  the  new  locomotives  of  the  New  York 
Central,  allows  the  utilization  of  the  available  space  in  an  excellent 
manner,  by  laying  the  pole  axis  horizontally  and  leaving  all  the 
height  for  the  armature  and  commutator  diameter.  The  whole 
length  of  the  car  axle  is  free  for  the  armature  as  the  field  and 
brush  yokes  are  closed  outside  the  wheels.  Almost  all  direct-cur- 
rent motors  have  six  to  twelve  coils  per  slot,  which  means  a  num- 
ber of  commutator  bars  equal  to  three  to  six  times  the  number  of 
slots,  which  makes  them  cheaper  and  safer  than  three-phase  motors 
for  which  a  large  number  of  slots  is  desirable  in  order  to  obtain  a 
good  power  factor. 

The  power  factor  of  three-phase  motors  is  kept  high  by  using 
high  speeds  and  low  periodicities,  which  render  generators  and 
transformers  more  expensive,  but  are  favorable  for  the  line.  For 
railways  with  the  exception  of  high  speed  lines  only  periodicities 
lower  than  25  are  suitable.  For  given  volume  and  rotor  diameter, 
nearly  closed  slots  produce  a  better  power  factor  than  closed  slots. 
By  using  a  three-phase  commutator  on  the  rotor,  the  phase  displace- 
ment, which  increases  the  first  cost  of  the  whole  plant,  may  be 
almost  entirely  compensated. 

The  power  factor  of  single-phase  commutator  motor  equals  usu- 
ally or  even  excels  that  of  three-phase  motors  and  reaches  values  of 
0.95  or  more.  But  it  is  necessary  or  advisable  to  use  frequencies 
of  25  and  less  and  small  air-gaps  which  may,  however,  be  somewhat 
larger  than  with  three-phase  motors.  The  ratio  field  ampere- 
turns*  to  armature  ampere-turns  must  be  small,  f.  i.,  20  to  27; 
for  the  repulsion  motor  this  ratio  is  changed  at  will  by  shifting 
the  brushes.  For  the  series  motor  the  normal  speed  must  be  equal 
to  one  and  one-half  to  two  and  one-half  times  the  synchronous  speed 
(Westinghouse  1.8  times)  and  the  cross-field  must  be  compensated. 

4.  The  old  Ganz  motors  built  15  years  ago  had  an  armature  voltage  30  per 
cent  higher  than  the  field  voltage,  and  with  them  was  used  a  switch  to  vary 
the  number  of  field  coils;  a  transformer  for  the  exciting  current  is  also 
mentioned  in  the  patent. 


132 


NIETHAMMER:     ELECTRIC    TRACTION. 


The  series  motor  which  is  built  with  many  poles  in  comparison  with 
the  repulsion  motor  increases  continuously  its  power  factor,  when 
the  speed  surpasses  synchronism,  whilst  the  repulsion  motor  has  its 
maximum  near  synchronism.  For  partial  loads  the  power  factor 
of  the  repulsion  motor  is  better,  for  normal  ?peed  there  is  no  essen- 
tial difference.  By  inserting  a  series  transformer  in  the  armature 
circuit  of  the  compensated  motor,  one  may  obtain  cos  <j>  =  1  for 
various  speeds. 

Table  III  gives  an  interesting  comparison  of  power  factor  and 
efficiency  for  three-phase  motors  and  various  methods  of  regulating 
them : 

TABLE    III. 


Half  speed. 

Full  speed. 

Concatenated 
motors. 

Variable 
number  of 
poles. 

Rotor 
resistance. 

Primary 
compen- 
sator. 

Variable 
frequency. 

Efficiency        81 
88 

- 

- 

43 

59 

—  I    Same 
87  f  motor. 

86 



74 



85 

75 

80 

_ 

_ 

__ 

90 

81 

86 







93 

86 

89 

— 

— 

— 

Power  factor  85 

60 

60 

85 

75 

85 

93 

77 

84 

93 

85 

93 

With  light  loads  the  power  factor  of  three-phase  motors  is  usu- 
ally very  poor,  and  the  mean  value  is  sometimes  as  low  as  0.5.  For 
starting  however  the  cos  <f>  is  0.8  to  0.95.  The  opposite  is  the  case 
for  single-phase  motors,  the  power  factor  at  starting  is  extremely 
low,  about  0.3,  increasing  with  speed  and  decreasing  with  load. 

Of  all  motors  the  direct  current  shows  by  far  the  smallest  losses 
in  the  motor  itself  when  starting  with  same  torque,  mainly  because 
the  iron  losses  are  zero  at  standstill  and  the  starting  current  is  least 
for  a  given  torque.  From  this  fact  it  results  that  a  direct-current 
motor  heats  least,  when  frequently  started. 

The  following  Table  IV  gives  a  comparison  of  the  motor  losses  at 
starting  for  various  types  of  motors  and  starting  arrangements. 


JflETHAMMER:     ELECTRIC    TRACTION. 


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134  NIETHAMMER:     ELECTRIC    TRACTION. 

Since  in  the  direct-current  motor  most  of  the  losses  are  produced 
far  away  from  the  motor  surface,  the  capability  for  radiating  heat 
is  better  for  the  alternate-current  motor  and  best  for  the  three- 
phase  machine.  For  equal  losses  the  difference  in  favor  of  the 
three-phase  motor  may  amount  to  25  per  cent.  The  distributed 
winding  is  also  better  for  cooling  than  the  mummified  concentrated 
field  coils,  for  which  latter  copper  strips  on  edge  are  best 

In  heavy  locomotives  or  motor  cars  for  high  acceleration,  it 
may  occur  that  there  is  not  sufficient  space  for  the  necessary  motor 
capacity  at  a  predetermined  rise  of  temperature.  This  limit  is  much 
sooner  reached  by  three-phase  and  single-phase  motors  than  by 
direct-current  motors,  and  of  all  motors  concatenation  is  worst 
in  this  respect.  In  extreme  cases  artificial  cooling  becomes  neces- 
sary. The  air  of  the  running  train  may  be  directed  by  special  pipes 
and  chimneys  on  the  surface  of  the  motors  and  starters.  If  it  is 


Ifto.  12. —  G.  E.  co.  MOTOR. 

possible  to  nse  openings  covered  by  gauze  or  perforated  sheets  at 
both  ends  of  the  motor,  one  may  drive  an  air  draught  through  the 
motor  by  the  ventilating  ducts  of  the  armature,  thereby  throwing 
the  heated  air  to  the  outer  surface.  The  new  G.  E.  motors  for 
the  New  York  Subway  are  ventilated  similar  to  Fig.  12  by  means 
of  air  entering  near  the  back  bearing  and  passing  through  armature 
ducts  of  variable  breadth  over  the  field  coils  and  escaping  through 
holes  in  the  yoke.  The  waste  air  of  the  universally  used  air- 
brake may  also  serve  for  cooling  purposes;  the  pressure  of  the  air 
must,  however,  be  kept  very  low  to  avoid  the  creeping  of  oil.  If 
there  is  sufficient  space  on  the  shaft,  there  may  be  added  a  fan  to 
the  motor.  Eeichel  proposed  to  install  these  fans  inside  the  second- 
ary motors  of  a  concatenated  group,  and  to  cool  the  main  motors 
from  these  fans. 

There  are  other  means  for  saving  space:     Siemens  &  Halske 
(German  patent  131,299)  propose  to  put  the  commutator  outside 


NIETHAMMER:     ELECTRIC    TRACTION. 

the  car  frame  to  leave  all  the  space  inside  available  for  the  armature. 
In  this  case,  however,  the  axle  must  be  hollow  and  many  connec- 
tions through  the  bearings  are  necessary.  This  scheme  may,  how- 
ever, be  much  better  realized  for  the  three  slip  rings  of  three-phase 
motors,  as  may  be  seen  from  Fig.  13,  which  shows  the  very  interest- 
ing concatenated  motors  of  Ganz  and  Company  for  the  new  Valtel- 
lina  locomotives.  (Each  motor  for  600  horse-power,  225  revs.  p. 


135 


13.  —  CONCATENATED   MOTOB,  VALTELLINA  LOCOMOTIVE. 


min.,  concatenated  500  horse-power,  112  revs.  p.  min.,  15  periods, 
3000  volts.)  To  best  utilize  the  given  height,  the  projecting  poles 
of  direct  current  and  single-phase  motors  must  be  arranged  at  45 
deg.  on  an  octagonal  frame  with  two  sides  horizontal;  the  most 
favorable  design  for  getting  a  large  armature  diameter  is  to  use  a 
bipolar  frame  putting  the  poles  horizontally  and  closing  the  yoke 
with  its  bearings  outside  the  frame  as  is  done  by  the  General  Elec- 


136  NIETHAMMER:     ELECTRIC    TRACTION. 

trie  Company  for  the  New  York  Central  motors.  Kandd  cuts  off 
a  segment  of  the  cylindrical  stator  iron  of  three-phase  motor  at  the 
lower  side.  (Fig.  13.)  On  locomotives  there  is  sometimes  suffi- 
cient space  to  put  the  motors  above  the  car  truck,  the  design  being 
much  simplified  thereby.  There  are,  in  fact,  cases  where  the  motors 
may  be  of  the  open  type,  if  they  are  well  protected  inside  the 
car  box  (Jungfrau  locomotives).  As  soon  as  it  becomes  possible 
to  build  reliable  ball  bearings,  these  may  be  used  to  reduce  the  space 
absorbed  by  the  bearings.  The  last  expedient  in  cases  of  limited 
space  consists  in  insulating  the  motors  by  heat  and  fireproof  mate- 
rials, such  as  mica  and  asbestos,  and  allowing  a  temperature  rise 
of  100  deg.  or  more,  though  the  commutators  will  hardly  with- 
stand these  temperatures  continuously. 

The  starting  torque  of  motors  for  high  accelerations  may  be  three 
to  ten  times  larger  than  the  torque  for  free  running,  whilst  for  slow 
speed  trains  there  is  no  great  difference  between  these  two  torques. 
The  best  motor  for  accelerations  higher  than  0.5  m  (per  sec.)2  is 
undoubtedly  the  direct  current  motor  which  starts  very  economi- 
cally against  any  torque  taking  less  than  two  and  one-half  times 
the  normal  current  for  three  times  the  normal  torque.  All  three- 
phase  railway  motors  in  actual  service  have  low  accelerations, 
smaller  than  0.3  m  (per  sec.)2;  the  large  locomotives  and  motor 
cars  on  the  Valtellina  lines  have  only  0.16,  though  tests  were  maclo 
up  to  0.45  m  (per  sec.)2.  Three-phase  motors  can  yield  specially 
high  starting  torques  only  by  adopting  complicated  switching  de- 
vices (mesh-star  connection)  or  heavy  regulating  transformers,  or 
by  sacrificing  the  best  running  conditions  (bad  power  factor  for 
free  running).  This  holds  specially  good  for  lines  with  very 
variable  grades.  Concatenated  motors  give  only  50  to  70  per  cent 
more  maximum  torque  than  the  primary  motor  alone  if  one  does 
not  increase  the  motor  voltage  for  concatenated  working.  It  is, 
therefore,  reasonable  never  to  switch  concatenated  motors  in  mul- 
tiple, but  to  leave  the  secondary  motors  idle  for  full  speed.  More- 
over the  acceleration  up  to  50  per  cent  of  synchronism  must  bo 
double  of  the  value  after  50  per  cent  of  synchronism  which  is 
also  true  for  the  mesh-star  connection. 

The  starting  torque  of  the  single-phase  motor  is  for  a  given 
voltage  the  highest  possible  torque  just  as  for  the  direct-current 
motor.  On  account  of  sparking  difficulties  and  self-induction,  the 
maximum  torque  is,  however,  smaller,  but  may  be  three  to  five 


NIETHAMMER:     ELECTRIC   TRACTION.  137 

times  the  normal  torque  for  well-designed  types.  The  starting 
current  is  nearly  entirely  wattless,  but  is  only  about  two  to  twj 
and  one-half  times  normal  current  for  three  times  the  normal 
torque.  When  starting  very  slowly  with  a  large  torque  by  a  strong 
field,  the  short-circuit  effect  under  the  brushes  may  burn  out  the 
motor.  The  torque  of  a  single-phase  motor,  which  is  30  per 
cent  smaller  than  that  of  a  corresponding  direct-current  motor 
is  not  constant  as  is  true  with  direct  and  three-phase  cur- 
rent machines,  but  varies  between  a  maximum  and  zero  with  double 
the  periodicity  of  the  line  current.  The  mean  value  of  the  torque 
is  only  half  of  the  maximum,  which  fact  is  very  important  for  the 
limit  of  slipping  of  the  wheels.  The  wheels  slip  when  the  mean 
useful  torque  is  only  half  of  the  maximum  torque  which  is  propor- 
tional to  the  adhesion  of  the  wheels.  This  limit  will,  however,  be 
reached  only  in  very  few  practical  cases. 

The  starting  torque  of  the  direct-current  series  motor  is  inde- 
pendent of  the  terminal  voltage,  whilst  the  torque  of  the  three-phase 
and  single-phase  motor  is  proportional  to  the  square  of  the  line 
voltage.  This  fact  is  specially  dangerous  for  starting  several  trains 
at  a  time  on  a  steep  grade.  The  single-phase  commutator  motors 
have  such  a  high  starting  torque  that  they  may  do  their  service, 
in  emergency  cases,  with  40  per  cent  of  the  full  line  voltage.  A 
disadvantage  with  the  three-phase  motor  is  due  to  the  fact  that  its 
breakdown  torque  occurs  at  a  slip  of  about  10  per  cent  coming  to 
standstill  when  overloaded  and  absorbing  a  high  wattless  current 
and  developing  no  torque  and  thus  being  liable  to  be  burned  out  in 
that  way. 

For  frequent  starting  the  watt  consumption,  or  economy  of  the 
whole  starting  period,  that  means  the  efficiency  of  acceleration,  is 
of  utmost  importance.  Direct-current  equipments  are  started  by 
series  parallel  control,  resistances  are  in  circuit  only  for  a  short 
time  as  the  motors  accelerate  a  long  time  without  resistances.  In 
principle  the  single-phase  motor  can  be  started  with  the  smallest 
losses,  as  they  need  no  resistances.  Starting  transformers  absorb, 
however,  continuously  a  certain  amount  of  energy  and  the  ef- 
ficiency of  the  motor  itself  is  low.  The  most  economical  way  of 
stating  consists  in  brush  shifting  (Brown,  Boveri  &  Cie).  The 
following  Tables  V  and  VI  contain  a  comparison  of  the  starting 
losses  of  various  systems : 


138  , 


NIETHAMMRR:     ELECTLtLV    TRACTION. 


TABLE   V. 

Total  starting  losses  for  one  entire  trip  of  an  elevated  train  of 
about  160  tons,  distance  about  1300  m,  mean  speed  =  30  km  p.  h. 


Direct 
current 

Three-phase. 

Single-phase 
commutator 
motors  (start- 

1 

Sgj 

parallel 
2  motor- 
groups. 

JS 
A 

| 

.a 

11 

a  o 

IN 

ing  trans- 
former or 
brush  shift- 
ing). 

a 

1 

OS  * 

33 

i 

o 

>• 

Mean  kw  hours  on  car  .... 

1.00 

1.85 

1.50 

1.17 

1.10 

0.90  to  1.20 

Mean  kvA  hours  on  car  .  . 

1.00 

1.55 

1.85 

1.67 

1.55 

1.10  to  1.50 

For  smaller  distance  the  values  become  worse  for  three-phase 
equipments  and  better  for  single-phase  motors. 


VIETHAMMER:     ELECTRIC    TRAGTIOM. 


139 


s 


lUI 

Isle 


II  111 

g  g  co  ,jj  O 

9-0  C-g  o 
grtOgg 

Psr 


111! 

lisfl 

fsgjS 

I  Sal 


1 


140 


NIETHAMMER:     ELECTRIC    TRACTION. 


Changing  the  direction  of  rotation  is  easily  done  for  direct  and 
single-phase  current  motors  by  crossing  the  connections  of  the 
armature;  for  high- voltage  single-phase  motors  this  ought  to  be 
arranged  in  the  low-voltage  secondary  of  a  series  transformer 
(Fig.  9)  or  a  safe  reversing  oil  switch  becomes  desirable.  Three^ 
phase  motors  may  be  reversed  by  interchanging  the  primary  wires, 
whilst  the  repulsion  motor,  whose  armature  is  only  in  inductive 
connection  with  the  line,  must  be  reversed  either  by  shifting  the 
brushes  through  about  a  polepitch  (Brown,  Boveri  &  Company)  or 
by  shifting  the  line  connections  to  the  stator  winding  by  about  a 
polepitch  or  by  using  two  primary  windings. 

The  direct  current  and  the  single-phase  series  motor  vary  in 
speed  automatically  about  inversely  proportional  to  the  load  with 
the  effect  that  for  variable  torque  the  input  and  current  consump- 
tion does  not  materially  fluctuate,  though  this  property  is  not  used 
to  its  full  extent  in  the  direct-current  motor,  as  may  be  seen  from 
the  following  table: 

TABLE  VII. 


Current  

1.9 

1.6 

1 

0.78 

0.58 

0.88  of  normal 

Speed  

0.75 

0.90 

1.0 

1.15 

1.40 

1.90  for  direct  current. 

Speed 

0  70 

1  0 

1  80 

1  8 

Torque  

2  6 

1.8 

1  0 

0  60 

0  80 

0  10  for  direct  current 

Torque  

1.65 

1  0 

0  70 

0  50 

0  85  for  single-phase 

Output  

1.9 

1.6 

1.0 

0.73 

0  58 

0  88  for  direct  current 

1.2 

1.0 

0.92 

0.90 

0.88  for  single-phase. 

The  three-phase  motor  and  direct-current  shunt  motor  have  prac- 
tically constant  speeds  for  all  loads  and  grades.  On  long  lines  with 
constant  grades  or  on  mountain  railways  this  quality  is  no  direct 
disadvantage,  as  the  timetable  is  independent  of  the  length  of  the 
trains  and  the  motorman  may  quietly  leave  his  regulating  switches 
alone  all  along  the  trip.  One  may  even  state  that  the  series  motor 
ir.  a  certain  sense  is  unable  to  make  up  for  delays  which  usually 
occur  with  overloaded  trains,  in  which  latter  case  the  series  motors 
diminishes  its  speed.  But  practice  proves  that  the  motorman  can 
easily  avoid  delays  by  making  the  best  of  the  variable  speed  charac- 
teristic of  the  series  motor  according  to  the  variable  grades  of  hi* 
line.  Of  course  on  three-phase  lines  the  main  current  may  bo 
interrupted  for  intervals,  either  to  increase  speed  when  descending 


NIETHAMMER:     ELECTRIC    TRACTION.  141 


or  to  reduce  speed  when  ascending.  Concatenated  motors 
in  themselves  an  additional  possibility  of  varying  the  schedule  time. 
The  inherent  constant  speed  quality,  however,  means  high  current 
consumption  on  grades  and  when  starting  compared  with  series 
motor  characteristics.  Moreover  the  direct-current  motor  has  very 
economical  means  for  speed  variation  through  wide  ranges  and 
the  single-phase  motors  possess  this  quality  even  to  a  higher  degree. 

Speed  variation  of  the  three-phase  motor  is  possible  by  one  of  the 
following  methods: 

1.  Ohmic  resistances  inserted  into  the  rotor  circuit,  the  regulation 
of  speed  depends,  however,  from  the  torque  used  for  a  given  resist- 
ance and  is  very  uneconomical.  Large  resistances  become  neces- 
sary and  small  speeds  at  small  torques  are  hardly  possible.  The 


Line 


Starting  Rheostat 

Fra.  14. —  CONCATENATED  MOTOR  CONNECTIONS. 

higher  the  resistance,  the  more  the  three-phase  motors  acquire  the 
variable  speed  quality  of  the  series  motor. 

2.  Concatenation  of  motors  which  has  been  admirably  perfected 
by  Ganz  &  Company.  This  company  uses  double  motors  in  one  frame 
(Fig.  13)  uniting  primary  and  secondary  motors  on  one  shaft  need- 
ing only  three  slip-rings  for  both  motors  (Fig.  14).  The  secondary 
motor  is  never  in  circuit  for  full  speed  and  may  be  specially  di- 
mensioned for  concatenation.  The  well-known  reproaches  made 
against  concatenation  are :  Bad  power  factor  and  bad  efficiency  for 
half  speed  (see  Table  III),  increase  of  weight,  space  and  heating. 
The  maximum  torque  of  concatenated  motors  is  rarely  more  than 
50  per  cent  greater  than  that  of  one  primary  motor.  The  starting  and 
switching  devices  are  rather  complicated.  Ganz  &  Company  have  de- 
cidedly reduced  these  difficulties  to  a  minimum  by  building  the 
double  motors  and  by  using  a  frequency  of  15  periods.  Efficiency  and 
power  factor  are  both  as  high  as  93  per  cent  (without  gears)  for  full 


142 


NIETHAMMER:     ELECTRIC    TRACTION. 


speed;  85  per  cent  efficiency  and  77  per  cent  power  factor  for  half 
speed ;  including  gear  loss  the  efficiency  is  still  80  per  cent  for  half 
speed.  Such  an  equipment  is  certainly  not  inferior  to  a  single-phase 
car  for  full  and  half  speeds.  The  Ganz  motors  have  very  high  over- 
load capacities  enabling  them  to  exert  high  drawbar  pulls  in  tandem 
connection.  The  complication  of  the  car  wiring  and  of  the  starting 
devices  has  been  avoided  by  using  only  three  sliprings  for  two  motors 
and  by  adopting  very  simple  and  safe  liquid  resistances  (Fig.  15). 
In  recent  tenders  Ganz  &  Company  propose  only  one  secondary 
motor  for  three  primary  motors  reducing  the  dead  weight 
materially. 

Brown,  Boveri  &  Cie  have  two  heavy  three-phase  locomotives  for 
the  Valtellina  line  under  construction.  The  two  motors  of  each  have 


FIG.  15. —  LIQUID  RESISTANCE,  GANZ  oo. 

450  horsepower  and  will  be  regulated  by  varying  the  number  of  poles 
from  16  to  8 ;  drawbar  pull  6000  kg  for  37  km  an  hour  and  3500  kg 
for  74-  km,  maximum  pull  for  half  speed  9000  kg.  This  scheme 
promises  higher  efficiency,  higher  torque  for  half  speed,  and  less 
space  than  concatenation.  These  motors  need,  however,  5  or  6  slip- 
rings  per  motor,  if  resistances  have  to  be  in  the  rotor  circuit  above 
and  below  50  per  cent  of  synchronism.  The  resistances  will  be 
metallic  in  this  case,  not  liquid.  The  type  of  winding  for  varying 
the  number  of  poles  must  be  a  multiple  parallel  loop  winding  with 
2X3  terminals  (Fig.  16).  The  winding  pitch  is  only  60  to  75  per 
cent  of  the  polepitch  at  the  high  speed  and  120  to  150  per  cent  of  the 
polepitch  at  the  low  speed.  Concatenated  motors  with  a  different 
number  of  poles  or  motors  with  more  than  two  numbers  of  poles  are 
surely  too  complicated  for  railway  work.  Variable  frequencies 


NIETHAMMER:     ELECTRIC    TRACTION. 


143 


would  certainly  give  a  very  economical  speed  variation,  but  the  com- 
plication and  the  increase  of  price  of  the  central  station  or  sub- 
station and  of  the  line  are  prohibitive. 

Brown,  Boveri  &  Cie  have  installed  a  variable  gear  ratio  on  their 
Burgdorf  Thun  locomotives,  which  makes  two  economical  speeds 
18  and  36  km  possible. 

Most  direct-current  equipments  possess  series-parallel  control 
either  with  two  or  four  motor  groups  giving  a  very  efficient  speed 
variation,  as  the  efficiency  at  half  voltage  or  a  quarter  voltage  is  only 


Zo       Zs 


-12  pole,  600  revs. 


-E|g — 8  pole,  750  revs. 
6  pole,  1000  revs. 
—4  pole,  1500  ret* 


|2  &  6  pole  8  &  4  pole 

1  7 

Two  separate 

windings 


FIG.  16. —  VAEIABLE  POLE  MOTOR  CONNECTIONS. 

1  to  5  per  cent  lower  than  for  full  voltage.  Double  commutators 
may  fulfill  the  same  purpose.  An  increase  of  speed  may  easily  be 
effectuated  by  shunting  the  field,  in  which  case  the  efficiency  is 
even  better  than  for  normal  speed.  Commutation  troubles  may, 
however,  prohibit  the  extensive  use  of  this  method. 

The  single-phase  commutator  motor  has  in  principle  the  most 
ideal  and  economical  as  well  as  the  most  uniform  speed  variation, 
by  the  use  of  regulating  transformers  in  the  primary  or  secondary 
circuit  of  the  motor  or  by  brush  shifting  or  by  varying  the  connec- 
tions between  the  line  and  a  series  of  taps  on  the  primary  winding. 
The  last  two  methods  are  specially  suitable  for  repulsion  motors. 


144  NIETHAMMER:     ELECTRIC    TRACTION. 

All  these  methods  work  with  good  efficiency  and  good  power  factor 
for  many  speeds.  The  continuous  losses  in  the  regulating  trans- 
formers, however,  decrease  the  total  efficiency  of  the  equipment. 
In  fact,  the  single-phase  regulation  is  not  more  economical  than  that 
with  a  four  motor  direct-current  equipment.  The  losses  are  spe- 
cially high  for  straight  single-phase  series  motors  using  an  auto- 
transformer,  a  potential  regulator  and  balancing  transformers. 
Series  transformers,  as  used  by  Winter  and  Eichberg  to  supply  only 
the  small  exciting  current  of  the  armature,  are  decidedly  preferable 
to  regulating  transformers,  and  the  best  scheme  seems  to  be  shifting 
of  the  brushes  or  the  shifting  of  the  taps  on  the  primary  winding 
as  used  for  repulsion  motors.  The  three-phase  motor  could  be 
very  economically  regulated  by  providing  a  polyphase  commutator 
on  the  rotor  and  a  three-phase  transformer  to  change  the  size  and 
phase  of  the  rotor  voltage,  but  this  scheme  is  somewhat  complicated 
and  is  not  suitable  for  railway  work. 

If  a  direct-current  series  motor  whose  field  connections  are  re- 
versed, is  separated  from  the  line  and  short-circuited  or  switched 
on  resistances,  it  will  act  as  a  brake,  the  effect  depending  upon  tho 
speed  and  the  resistance  in  circuit.  The  series  motor  is,  however, 
unable  to  return  energy  to  the  line.  By  arranging  a  small  exciter 
which  just  yields  the  small  exciting  voltage  of  the  series  winding 
and  the  full  exciting  current,  returning  of  energy  could  be  easily 
effectuated.  The  best  motor  for  energy  returning  is  the  direct- 
current  shunt  motor  which  acts  as  a  generator  without  making 
necessary  any  switching.  The  simple  field  regulation  enables  the 
shunt  motor  to  work  as  generator  and  motor  within  a  very  wide 
range  of  speed;  without  any  change  the  shunt  motor  works  also  on 
resistances  or  as  a  short-circuited  brake.  On  mountain  railways  the 
braking  on  resistances  is,  however,  rarely  desirable,  as  the  resist- 
ances on  the  locomotives  become  too  cumbersome  and  heavy  (i.  e.f 
2000  kg  on  an  11-ton  engine).  If  other  motor  cars  are  on  the 
line,  the  downgoing  shunt  motor  feeds  the  ascending.  If  there  is 
only  one  car  on  the.  line,  the  energy  returned  will  speed  up  the 
generators  and  will  be  only  troublesome.  One  may  provide  re- 
sistance, in  parallel  with  the  generators,  to  absorb  the  superfluous 
energy,  but  by  far  the  best  method  is  to  install  storage  batteries  in 
the  sub-stations  which  are  charged  by  the  descending  cars. 

The  three-phase  motor  has  braking  qualities  similar  to  those  of 
the  direct-current  shunt  motor,  but  throughout  a  very  restricted 
range.  The  three-phase  motor  returns  energy  only  for  speeds  above 


NIETHAMMER:     ELECTRIC    TRACTION.  145 

synchronism,  that  means,  within  a  very  narrow  range  and  the 
energy  cannot  be  stored  up.  Braking  on  resistances  independently 
from  the  line  is  only  possible  by  an  additional  exciter.  The  range 
of  returning  energy  may  be  somewhat  increased  by  applying  con- 
catenated motors,  but  this  advantage  must  be  very  expensively  paid 
for,  besides  the  fact  exists  that  a  short-circuited  concatenated  group 
only  acts  as  generator  between  50  and  75  per  cent  of  synchronism 
and  then  again  above  synchronism.  By  inserting  resistances  in  the 
rotor  of  the  secondary  motor  this  range  may  be  slightly  increased. 
On  level  lines  as  encountered  on  elevated  roads  not  more  than  10  per 
cent  of  the  stored  up  energy  can  be  returned  by  concatenated  motors. 
On  lines  with  many  steep  grades  and  dense  traffic,  the  returned 
energy  may  be  more  and  become  of  decided  advantage. 

For  mountain  railways  the  three-phase  motors  have  been  fre- 
quently used  (Jungfrau,  Gornergrat  &  Engelberg),  but  it  does 
seem  not  to  have  been  a  complete  success,  as  new  mountain  lines 
(Vesuvius,  Opcima  Triest)  are  not  equipped  with  three-phase  motors 
but  with  direct-current  shunt  motors.  The  main  reasons  are  that 
for  the  three-phase  motor  the  downgoing  speed  must  be  higher  than 
the  ascending  one  which  is  prohibited  by  most  railway  regulations 
and  that  the  energy  of  the  descending  car  cannot  be  stored  up, 
neither  of  which  reasons  is  applicable  to  the  shunt  motor.  There  are 
very  ingenious  schemes  for  perfecting  the  three-phase  motor  for 
steep  grades.  The  Maschinenfabrik  Oerlikon  switched  the  motors  on 
their  Jungfrau  locomotive  No.  3  in  the  upward  sense  for  going 
downward  in  such  a  way  that  the  primary  field  revolved  against  the 
rotor  rotation.  By  inserting  resistances  into  the  rotor,  in  which 
the  frequency  is  higher  than  in  the  line,  any  speed  between  stand- 
still and  full  speed  may  be  obtained,  but  the  resistances  must  dissi- 
pate twice  the  energy  braked  and  the  line  has  to  provide  just  as 
much  energy  for  descending  as  for  ascending.  The  next  step  was  to 
iise  a  special  direct-current  exciter  directly  connected  to  the  motor 
shaft  for  braking,  the  motor  works  as  a  three-phase  synchronous 
generator.  The  A.  E.  Gr.  had  arranged  a  storage  battery  for  th'e 
same  purpose  on  its  high-speed  car.  If  three-phase  currents  must 
be  used,  the  simplest  scheme  would  be  to  take  the  compensated  three- 
phase  motor  with  commutator  on  one  side  and  sliprings  on  the  other, 
which  acts  as  generator  at  will  (newest  Jungfrau  locomotive5  of 

5.  The  brushes  on  the  commutator  of  these  motors  are  automatically 
lifted,  when  the  locomotive  is  connected  to  the  line.  The  speed  may  be 
cut  down  to  5  per  cent  of  full  speed. 

ELEC.  RYS. 10. 


140  NIETHAMMER:     ELECTRIC    TRACTION. 

Brown,  Boveri  &  Company),  though  it  is  inferior  to  the  direct- 
current  shunt  motor. 

Those  single-phase  commutator  motors,  the  armature  and  field  of 
which  are  interconnected  directly  or  through  a  transformer,  may  be 
separated  from  the  line,  and  caused  to  work  on  resistances  as 
single-phase  generators  of  variable  frequency.  The  return  of 
energy  to  the  line  is  possible  onl}r  by  rather  complicated  switching 
devices,  such  as  changing  the  variable  speed  feature  into  a  constant 
speed  one  or,  in  other  words,  by  creating  a  shunt  motor  or  a  sepa- 
rately excited  motor.  This  may  be  done  practically  by  feeding  field 
and  armature  from  a  transformer  having  a  series  of  taps  which  are 
changed  according  to  speed  and  load.  (Fig.  17,  Union  motor.)  If 
the  repulsion  motor  is  driven  backwards,  it  acts  as  a  brake;  by 
varying  the  brush  angle  any  braking  torque  may  be  produced  and 
even  at  low  speeds  energy  may  be  returned  to  the  line. 


Pio.  17. —  CONNECTIONS  or  MOTOR  USED  AS  GENERATOR. 

For  returning  energy  at  speeds  from  the  highest  down  almost  to 
standstill,  the  most  perfect  system  is  a  direct-current  equipment 
with  two  double-commutator  motors,  with  a  combined  series  and 
shunt-field  winding  and  regulating  resistances  in  series  with  the 
shunt  field  and  in  parallel  with  the  series  field.  For  the  highest 
speed,  the  four  commutators  are  in  multiple  and  the  field  weakest ; 
for  the  lowest  speed,  all  commutators  are  in  series,  the  field  strong- 
est. This  scheme  is,  however,  too  complicated  for  practical  railway 
service. 

Motors  which  are  regularly  and  frequently  used  for  braking  pur- 
poses must  be  much  more  liberally  laid  out  and  they  are  more 
liable  to  injuries  than  those  used  simply  for  haulage. 

The  shunt  motor  which  has  several  very  valuable  features  for 
braking  and  speed  variation  has  the  great  fault  which  rather 
excludes  it  from  most  railway  services  in  that  it  is  almost  unsuitable 
for  parallel  running.  This  adverse  criticism  must  be  made  concern- 
ing all  motors  with  constant  speed  characteristics  including  the 
three-phase  motor.  If  by  chance  the  wheel  diameters  are  not 


NIETHAAIMER;     ELECTRIC    TRACTION. 


147 


identical  in  general,  if  the  slip  in  speed  is  not  equal  or  if  the  mag- 
netic characteristics  of  two  shunt  motors  or  of  two  three-phase 
motors6  are  slightly  different  (not  the  same  air-gap  or  not  the  same 
permeabilities),  one  motor  takes  more  of  the  whole  load  than  the 
other.  It  may  even  happen  that  one  motor  acts  as  generator,  deriv- 
ing its  energy  from  the  other  which  must  carry  the  whole  load, 
causing  a  break-down  and  throwing  the  locomotive  from  the  rails. 
This  has  actually  occurred  on  mountain  railways.  For  emergency 
cases  rail  tongs  must,  therefore,  be  provided  which  prevent  the  de- 
railing of  the  locomotive.  For  the  shunt  motor,  there  may  be  used 
the  following  remedies:  Two  shunt  regulators  may  be  used,  ono 
for  each  motor,  adjusted  in  a  manner  such  as  to  equalize  the  load. 
The  adjustment  is,  of  course,  different  for  an  ascending  and  a  de- 
scending car.  and  it  must  be  modified  before  reversing.  A  scheme 
installed  by  the  Austrian  Union  Company  on  their  locomotives  for 


Fio.  18.— EQUALIZING  SHUNT  MOTORS. 

Opcima-Triest  seems  to  possess  many  advantages  (Fig.  18).  The 
two  armature  terminals  of  same  polarity  are  connected  by  a  small 
regulating  resistance,  and  the  lever  of  this  resistance  is  grounded, 
the  rail  being  the  return  conductor.  By  adjusting  this  resistance 
which  takes  at  most  2  per  cent  of  the  whole  voltage,  the  load  in  any 
case  may  be  equally  distributed.  The  position  of  the  lever  is  differ- 
ent for  motor  and  for  generator  action.  The  automatic  breaker  in 
the  trolley  circuit  cannot  be  used  for  avoiding  overloads,  as  the  cur- 
rent does  not  flow  to  the  line  and  as  the  armature  circuit  is  not 
allowed  to  contain  a  circuit  breaker,  as  it  would  render  emergency 
braking  very  dubious.  Brown,  Boveri  &  Cie  arrange  a  friction 
clutch  between  each  motor  and  the  axle,  which  transmits  only  a 
certain  maximum  torque.  The  simple  remedy  of  using  only  motors 
in  series  is  not  to  be  recommended  as  on  steep  lines  it  happens  that 

6.  For  three-phase  motors  that  means  different  magnetizing  and  different 
short-circuit  current. 


148  NIETHAMMER:     ELECTRIC    TRACTION. 

one  wheel  slips  and  the  other  stands  still,  in  which  case  the  former 
motor  is  subjected  to  the  whole  voltage  and  may  burn  out. 

Cars  with  direct-current  equipments  may  be  run  on  lines  with 
variable  voltage,  if  the  motors  are  connected  only  in  series  on  one 
part  of  the  line  and  only  in  multiple  on  the  other,  or  by  adopting 
double  commutator  motors.  The  trolley  line  voltage  of  three-phase 
and  single-phase  cars  may  be  varied  at  will,  if  a  stationary  trans- 
former is  provided  on  the  car,  which  transformer,  however,  in- 
creases the  weight  of  the  equipment  considerably.  The  Austrian 
Union  Company  is  just  completing  a  suburban  single-phase  line, 
starting  from  Innsbruck,  which  is  fed  at  400  volts  inside  the 
town  and  at  2700  volts  outside.  Single-phase  cars  may  even  be 
run  over  direct-current  tracks,  though,  a  good  single-phase  motor 
usually  is  a  pretty  bad  direct-current  machine;  for  the  repulsion 
motor  this  is  a  specially  bad  case.  Moreover  the  primary  and  sec- 
ondary motor  voltage  rarely  agrees  with  the  direct-current  line 
voltage  and  a  special  set  of  starting  resistances  must  be  provided, 
or  the  single-phase  equipment  must  use  rheostatic  control,  which 
is  very  uneconomical.  Best  is  series-parallel  control  in  this  case. 

Motor  Gearing. 

In  most  cases  the  motors  drive  the  car  axle  by 

1  a  single  gear  of  cylindrical  tooth  wheels  with  ratios  of  1 : 1  to 
1 :  5  which  withstand  the  wear  of  8000  to  200,000  train-km.    In 
few  cases  one  finds 

2  cogged  wheels  (Alioth)  or  double  and  treble  threaded  worm 
gears   (Maschinenfabrik  Oerlikon),  which  in  some  cases  allow  a 
better  disposal  of  the  available  space.     For  very  low  speeds  double 
gear  becomes  necessary,  i.  e.f  Jungfrau  and  other  mountain  loco- 
motives. 

3.  The  direct  coupling  of  motor  and  axle  may  either  be 

(a)  rigid  (Central  London,  Siemens  &  Halske  high  speed  car, 
new  locomotives  for  New  York  Central)  or 

(b)  elastic,  by  means  of  a  hollow  shaft  and  a  flexible  coupling 
(Heilmann  Locomotive,  A.  E.  G.  high  speed  car,  Valtellina  locomo- 
tives of  Ganz  &  Company).    The  rigid  connection  of  the  armature 
on  the  car  axle  has  up  to  the  present  not  been  a  complete  success,  but 
the  method  with  the  hollow  shaft  and  coupling  is  decidedly  compli- 
cated and  entails  the  waste  of  much  precious  space.     Siemens  & 
Halske  support  the  frame  of  their  rigidly  connected  motors  from 
the  truck  by  means  of  springs,  by  which  the  bearings  are  pressed 


NIETHAMMER:     ELECTRIC    TRACTION. 


149 


against  the  axle  from  below,  an  oil  cushion  on  the  upper  half  of  the 
bearing  boxes  damping  vertical  shocks  of  the  frame.  From  Fig.  19 
one  may  get  an  idea  of  the  design  of  the  Valtellina  motors  for  250 


FIG.  19. —  VALTELLINA  GEABLESS  MOTOB. 

horse-power,  300  revolutions,  3000  volts,  with  a  hollow  shaft  and  a 
flexible  coupling.  The  new  550-hp  motors  of  the  General  Electric 
Company  are  rigidly  fixed  on  the  axle,  but  the  frame  may  freely 
move  in  the  vertical  direction,  as  the  motor  has  only  two  poles,  one 
at  each  side,  and  the  pole  shoes  have  plain  vertical  surfaces.  For 
motors  mounted  on  the  car  axle,  special  care  is  necessary  to  exclude 
oil  and  dirt  from  the  motor  windings. 

4.  Driving  by  cranks  and  connecting  rods, —  well  known  from 
steam  locomotives  —  was  probably  first  proposed  for  electric  loco- 
motives by  Eickemeyer,  and  first  used  by  Brown,  Boveri  &  Cie.  The 
location  of  the  motors  above  the  axle  is  decidedly  facilitated  by 
this  mode  of  driving.  Very  disagreeable  vertical  and  other  move- 
ments and  shocks,  such  as  are  incident  to  steam  driving,  can  hardly 
be  avoided  when  this  construction  is  used.  Ganz  &  Company  have 
laid  out  a  special  arrangement  for  their  new  Valtellina  locomotives 


PIG.  21.  LOCOMOTIVE  WITH  CONNECTING  BODS. 

(Fig.  20),  the  crank  turning  point  being  supported  in  such  a  way 
as  to  allow  vertical  movements.  The  General  Electric  Company 
possess  a  patent  on  the  arrangement  (Fig.  21),  in  which  two  double 


150 


NIETHAMHER:     ELECTRIC    TRACTION. 


WIETHAMMER:     ELECTRIC    TRACTION.  151 

commutator  motors  are  mounted  at  the  end  of  the  locomotive  and 
four  axles  are  joined  by  cranks  and  connecting  rods. 


Starters. 
For  starting  are  used 

(a)  Metallic  or  liquid  resistances  combined  with  series  parallel 
control ; 

(b)  Transformers  or  autotransformers  with  taps  or  potential 
regulators, —  mainly  for  single-phase  motors ; 

(c)  Brush  shifting  for  repulsion  motors  (Brown,  Boveri  &  Cie). 
The  last  method  is  undoubtedly  the  cheapest. 

Regulating  transformers  for  single-phase  motors  are  heavier  and 
more '  expensive  than  starting  resistances,  .even  if  high  iron  in- 
ductions (15,000  per  cm2)  and  high  copper  densities  (3  to  5  amp. 
per  mm2)  are  adopted.  They  should  be  submerged  in  oil  or  ar- 
tificially cooled  by  compressed  air.  If  series  transformers  (Fig.  8) 
are  used  for  the  armature  alone,  the  size  and  weight  are  materially 
reduced.  The  heaviest  are  the  potential  regulators  which  must  be 
provided  with  a  short-circuited  coil  to  neutralize  the  cross-field  or 
self-induction  of  the  armature.  They  allow,  however,  a  very  steady 
regulation,  and  avoid  all  contacts  liable  to  spark;  the  higher  the 
line  current,  the  smaller  is  the  range  of  voltage  control.  The 
main  difficulty  in  the  design  of  the  usual  regulating  transformers 
with  taps  is  due  to  the  necessity  for  a  reliable  switch  dial  which 
works  sparklessly.  The  best  scheme  seems  to  involve  a  solid  snap 
switch  which  interrupts  the  current  for  a  moment,  when  jumping 
from  one  tap  to  the  next  thus  avoiding  all  auxiliary  contacts  and 
the  short-circuiting  of  coils  and  eliminating  the  use  of  resistances 
or  inductances. 

For  various  reasons  three-phase  starting  resistances  must  be 
'heavier  and  more  voluminous  than  direct-current  starters.  To 
this  is  probably  due  the  fact  that  liquid  resistances  have  been 
•thought  more  desirable  for  three-phase  than  for  direct-current 
railways.  Though  at  first  sight  a  liquid  resistance  seems  to  be 
mechanically  much  poorer  than  solid  parcels  of  nickeline  strips  or 
eastiron  grids,  the  dimensions  of  which  may  be  very  much  reduced 
"by  forced  air  cooling  (Jungfrau  line)  or  by  placing  them  into  oil 
tanks,  the  designs  of  Ganz  &  Company  and  those  of  the  A.  E.  Gr. 
'high-speed  car  are  of  practical  interest,  and  the  first  mentioned 


152  NIETHAMMER:     ELECTRIC    TRACTION. 

design7  (Fig.  15)  has  operated  satisfactorily  for  years.  The  prin- 
ciple involved  in  their  construction  consists  in  using  stationary 
electrodes  within  a  tank  into  which  the  liquid  is  forced  either 
by  air  pressure  or  by  a  rotating  pump.  The  time  consumed  in 
starting  may  be  varied  by  regulating  the  air  pressure  or  by  adjust- 
ing a  throttle  valve  (Fig.  15).  The  electrodes  consist  of  solid 
parcels  of  iron  sheets  which  may  be  readily  replaced.  For  frequent 
starting  and  shunting  purposes,  the  liquid  tanks  must  be  very 
liberally  dimensioned;  it  is  desirable  that  the  motorman  control 
the  resistance  according  to  a  main  current  ammeter,  to  avoid 
current  rushes.  The  outer  surface  of  the  tank  is  provided  with 
cooling  ribs.  The  overload  capacity  of  liquid  starters  is  very 
high,  as  when  the  water  is  evaporating,  an  immense  amount  of  heat 
may  be  absorbed.  There  is,  however,  the  drawback  that  the  water 
level  may  oscillate  and  that  the  evaporated  water  must  regularly 
be  replaced  (2  liters  on  500  km  for  the  Valtellina  line).  On  very 
cold  days  freezing  is  possible.  To  avoid  a  heavy  current  rush 
before  short-circuiting  the  liquid  starter,  it  is  necessary  that  the 
electrodes  have  such  a  shape  as  to  finally  reduce  the  resistance  to 
a  value  less  than  that  of  the  armature. 
The  starting  switches  may  be, 

1.  Cylindrical  controllers  with  contacts  for  reversing  and  series- 
parallel  control,  and  for  the  control  of  resistances  or  transformer 
coils,  sometimes  provided  with  flat  dials  at  the  lower  end  for  field 
regulation. 

2.  Multiple  unit  control  with  a  series  of  single  switches  actuated 
by  electromagnets  or  by  compressed  air  pistons. 

3.  Liquid    starters. —  For    small    inputs,    the    cylindrical    con- 
trollers  are    in    almost   universal   use.      For    three-phase   equip- 
ments, they  become  heavier   and  more   voluminous,   on   account 
of   the   increased   number    of   contacts,   which   number   may   be 
somewhat  diminished  by  using  two-phase  rotors.     The  multiple- 
unit    system    has    been    developed    for    direct    current    by    the 
General    Electric    Company    (electromagnetic    switches),    by    the 
Westinghouse     Company    and     the     Siemens     Schuckert    Werke 
(electropneumatic  control),  for  single-phase  cars  by  the  Union  E. 
C-.  Berlin,  the  system  resembling  very  much  the  direct-current  con- 
trol of  the  G.  E.  Company.     The  electromagnets,  however,  must  be 

7.  Fig.  15  shows  the  original  design  of  the  Ganz  rheostat  which  has 
been  changed  somewhat  in  its  details;  p  is  the  throttle  valve,  k  the  short- 
circuiting  switch  of  the  rheostat. 


NIETHAMMER:     ELECTRIC    TRACTION.  153 

laminated,  and  for  the  primary  circuit,  high-tension  oil  switches 
must  be  used.  As  alternate-current  electromagnets  are  known  to 
have  various  bad  qualities,  it  seems  to  be  a  good  plan  to  propose 
direct-current  control  from  a  small  storage  battery  or  electropneu- 
matic  control  for  single-phase  cars.  For  three-phase  equipments 
multiple-unit  control  has  never  been  used  or  proposed,8  on  account 
of  its  being  rather  complicated.  Moreover  the  tendency  of  three- 
phase  railways  is  toward  locomotives  and  not  toward  the  use  of  a 
series  of  motor  cars  in  a  train.  On  account  of  the  many  wires  and 
contacts  for  three-phase  current  liquid  starters  with  pneumatic  con- 
trol have  come  to  the  front,  as  already  stated.  The  liquid  resistance 
does  away  with  the  great  number  of  contacts  and  the  sparking 
troubles  of  switches  for  heavy  currents,  allowing  a  very  steady 
regulation  and  occupying  only  a  moderate  amount  of  space. 
Several  single-phase  or  direct-current  motors  in  multiple  may  be 
equipped  with  one  common  starting  resistance  if  desired,  whilst 
this  arrangement  is  not  possible  with  three-phase  motors,  unless 
the  relative  position  of  all  parallel  rotors  is  continuously  identical, 
which  condition  seems  impossible  to  be  obtained.  When  this  is 
not  the  case,  the  rotors  may  be  partly  short-circuited  by  the  cross- 
connections. 

In  the  following  Table  VIII  I  have  tried  to  make  a  comparison 
of  the  weight  of  various  starting  devices. 

8.  There  are  several  patents  on  polyphase  multiple  control  granted  to 
the  G.  E.  Co.  four  years  ago. 


154 


NIETHAMMER:     ELECTRIC    TRACT '£ON. 


TABLE  VIII. 
a.  Direct  current. 


Builder. 

Motors. 

Weight  of  starting  devices  in  kg. 

Volts. 

H.P. 

Weight, 
kg. 

Krizik  Prague.... 

2x650 

4x30 

4x985 

Entire  electric  equipment  per  car  with- 
out motors:  1,560. 

Q  E  Co  ... 

500 

1x27 

700 

1  controller  and  resistance:  150. 

Alioth  

500 

2x81 

2x770 

Entire  electric  equipment  without 
motors:  960. 

Alioth  

500 

4x88 

4x890 

Entire  electric  equipment  without 
motors:  3,600. 

Westinghouse.... 

500 

2x55 

2x1,860 

2  controllers  and  resistances:  660. 

Q.  E  Co  

500 

2x65 

2x1,600 

2  controllers  and  resistances:  600. 

Alioth  

500 

2x65 

2x1,850 

Entire  electric  equipment  without 
motors:  4,100. 

G.  E.  Co  

500 

2x80 

2x1,800 

2  controllers  and  resistances:  700. 

4x600 

4x125 

4x8,600 

Entire  electric  equipment  without 
motors:  6,600. 

Westinghouse.  .  .  . 

500 

2x150 

2x2,400 

2  controllers  and  resistances:  750. 

G  E  Co       .... 

600 

2x165 

2x2,400 

Weight  of  whole  control  apparatus: 
1,000  (multiple  unit). 

Westinghouse.  .  .  . 

600 

2x150 

2x2,400 

Weight  of  whole  control  apparatus 
(including  small  battery):  800  (mul- 
tiple unit). 

Brown,  Bo  veri.... 

600 

b.  Thr 

2x25 

ee-phase 

2x830 

currents. 

Entire  electric  equipment  without 
motors:  1,500. 

Brown,  Boveri  .... 

750 

2x150 

2x4,000 

2  controllers  and  starting  resistances: 
2,000. 

Siemens  &  Halske 

10,000 

2x200 

2x4,100 

Entire  electric  equipment  without 
motors:  8,800  (metallic  resistances). 

Siemen  &  Halske. 

10,000 

4x250 

4x4,000 

Metallic  resistances  5,000,  controllers 
4,800,  transformers  for  10,000  1  1,000 
volts:  12,000. 

AEG  

10,000 

4x250 

4x8,200 

Liquid  starters  4.800,  transformers 
6,400. 

8,000 

2x600 

2x12,500 

Entire  electric  equipment  without 
motors:  7,000  (liquid  starters). 

500 

c.  Sine 

1x27 

jle-phast 

1x800 

!  current. 

Transformer  800. 

Union  

2,700 

2x50 

2x1,240 

Transformer  2,700  1  400  volt:  680  kg  (oil 
type),  regulating  transformers: 
2  x  315  kg. 

Union  

6,000 

2x100 

2x2,860 

Regulating    transformers    1,100     kg, 
whole   electric   equipment  without 
motors  1,800  kg. 

Oerlikon  

14,000 

4x145 

4x8,000 

Transformers  5,600  kg,  apparatus  and 
switches  800,  trolley  1,200. 

Oerlikon  

14,000 

4x200 

4x3,400 

Transformers  8,400  kg,  apparatus  and 
switches  900,  trolley  1,200. 

For  the  repulsion  motor  with  brush  snifting  no  special  starting  devices 
are   necessary. 


NIETHAMMER:     ELECTRIC    TRACTION.  155 

For  operating  whistles  and  brakes,  electricity  is  not  directly 
applicable,  and,  in  most  cases,  compressed  air  must  be  used  for 
this  purpose.  The  air  brakes  and  the  main  controllers  should  be 
so  interconnected  that  applying  the  brakes  instantly  interrupts 
the  main  current.  The  air  compressor  should  be  driven  electrically 
and  should  run  noiseless,  which  latter  condition  seems  to  be  most 
easily  obtained  when  slide  valves  are  used.  On  steep  grades  there 
should  be  provided  electromagnetic  rail  brakes,  or  a  braking  rack 
should  be  placed  along  the  rails.  To  avoid  derailing  on  mountain 
railways,  rail  tongs  are  desirable.  In  order  to  eliminate  the  pos- 
sibility of  racing  on  steep  grades,  there  should  be  provided  a 
device  which  prevents  the  motorman's  leaving  his  car  or  train  if 
he  has  not  first  put  the  controller-handle  on  the  short-circuit  brak- 
ing point. 

Although  universally  used,  the  scheme  of  lighting  the  trains 
directly  from  the  trolley  line  is  a  bad  one.  Periodicities  below  40 
give  a  flickering  light,  unless  very  low  voltages  and  thick  fila- 
ments are  used.  The  question  of  train  lighting  is,  however,  not  so 
important  as  to  render  useless  a  system  which,  though  defective 
ii:  this  one  respect,  is  first  class  in  all  others,  it  being  possible,  in 
any  event,  to  provide  for  lighting  the  train  from  some  source  in- 
dependent of  the  trolley  circuit. 

Current  Collectors  and  Line. 

The  problem  of  collecting  current  from  the  line  is  one  of  the 
most  difficult  in  electric  traction.  While  direct-current  and  single- 
phase  equipments  using  the  rails  as  return  require  but  a  single  con- 
ductor, three-phase  and  certain  other  three-wire  cars  necessitate  at 
least  two-line  wires,  which  drawback  to  such  equipments  in  some 
cases  is  so  serious  as  to  prohibit  their  use.  The  two  conductors  may 
be  installed  either  above  the  center  of  the  line  beside  each  other  in 
the  same  height  or  in  different  heights,  or  beside  the  line  one  above 
the  other,  the  current  collector  sliding  from  the  side,  or  one  wire  may 
be  on  each  side  of  the  line  (Fig.  22).  The  lateral  current  collection 
avoids  the  oscillation  of  the  current  collector,  arising  from  the 
•deflection  of  the  wire,  but  if  the  wires  hang  above  each  other,  short- 
circuits  may  easily  occur.  As  far  as  my  experiences  go,  there 
•seems  to  be  no  difficulty  in  collecting  current  for  single-phase  lines 
for  voltages  up  to  6000.  For  three-phase  lines  the  limit,  as  derived 
from  the  experiences  on  the  Valtellina  line  with  humid  tunnels, 


156 


NIETHAMMER:     ELECTRIC    TRACTION. 


sharp  curves  and  steep  grades  seems  to  be  3000  volts.  For  equal 
line  voltage  the  voltage  drop  of  the  line  which  influences  very 
much  the  starting  torque  of  alternate-current  motors  is  much 
greater  for  three-phase  and  single-phase  currents  than  for  direct 
current  and  on  account  of  phase  displacement,  the  equivalent  cur- 
rent is  also  higher.  The  increase  of  voltage  drop  is  the  higher, 
the  higher  the  frequency.  The  resistance  of  the  iron  rails  foi 
alternating  current  amounts  to  between  3  and  15  times  the  value 
for  direct  current  on  account  of  the  skin  effect.-  A  high  voltage 
drop  in  the  rails  causes  electrolytic  effects  for  direct  current  and 


czir — 


FIG.  22. —  HIGH  POTENTIAL  OVERHEAD  CONSTRUCTION  OF  SIEMENS  &  HALSKE. 

telephone  or  telegraph  disturbances  for  direct  and  alternate  cur- 
rents. For  this  reason  special  return  wires  may  become  necessary 
(fourth  rail),  which  must  be  frequently  connected  to  the  main  rails, 
and  which,  for  alternate  currents,  should  be  as  close  to  the  other 
trolley  wires  as  possible.  Kapp  proposed  to  place  boosting  dynamos 
or  transformers  between  two  consecutive  rails  at  various  spots. 
The  Maschinenfabrik  Oerlikon  is  using  a  separate  return  wire 
along  the  rails  and  puts  the  boosting  transformers  into  this  special 
wire,  the  primary  of  the  transformer  being  in  the  overhead  con- 
ductor. In  this  way  the  voltage  drop  of  the  return  wire  which 


NIETHAMMER:     ELECTRIC    TRACTION. 


157 


is  regularly  connected  to  the  rails  is  reduced  to  naught  and  the 
drop  is  transferred  to  the  overhead  wire,  the  drop  of  which  is 
correspondingly  increased.  If  high  trolley  voltage  or  the  boosting 
scheme  of  Oerlikon  is  used,  railbonds  are  no  longer  a  necessity; 
they  are,  therefore,  omitted  in  a  new  single-phase  line  of  the 
Austrian  Union  Company  with  2700  volts. 

The  current  collectors  used  nowadays  are: 

1.  The  trolley  wheel  with  overhead  conductor  consisting  of  a 
circular  or  an  8-shaped  profile-wire,  suitable  for  about  200  amp. 
voltages  below  1000,  and  speeds  not  exceeding  80  km  an  hour. 
The  trolley  wire  may  hang  just  above  the  line  or  on  the  side  of 
it  (lateral  trolley),  as  the  trolley  arm  is  hinged  upon  a  vertical  bolt; 
the  height  of  the,  wire  above  the  line  may  also  vary  considerably. 
A  disadvantage  is  the  hammering  of  the  wheel  against  the  wire  and 
the  frequent  derailing,  which  may  be  somewhat  reduced  by  using 


Section  c-d 


FIG.  23. —  TROLLEY  SHOE. 

very  light  and  elastic  trolley  arms,  the  movements  of  which  may 
be  damped  by  various  springs  or  air  and  oil  cushions.  For  cur- 
rents greater  than  200  amp.,  two  trolleys  may  be  adopted. 

The  wheel  may  be  replaced  by  a  sliding  shoe  on  the  end  of  the 
trolley  arm  (Fig.  23),  the  inside  of  which  may  be  covered  with 
aluminum  (Jungfrau  railway).  The  ability  to  collect  current  is 
increased  in  this  way,  but  the  deterioration  of  the  wire  is  augmented. 

2.  The  sliding  bow  consists  of  a  tube  of  brass  or  aluminum  con- 
taining a  V-shaped  groove  and  stands  with  axis  perpendicular  to 
the  trolley  wire.  To  get  a  larger  surface  of  contact,  Brown, 
Boveri  &  Company  have  given  a  triangular  cross-section  to  the  bow 
(Fig.  24),  one  plain  surface  of  which  is  continuously  on  the  wire. 
The  inside  of  the  tube  may  be  filled  with  grease.  The  bow  may 
carry  100  amp.  for  voltages  up  to  10,000  or  200  amp.  for  low 
voltages;  sliding  on  two  overhead  wires  300  amp.  may  be  safely 


158  NIETHAMMER:     ELECTRIC    TRACTION. 

collected  at  1000  volts  or  less.  The  line  equipment,  especially  the 
overhead  switches,  are  much  simpler  for  the  bow  than  for  the 
trolley  wheel;  there  is  no  derailing.  The  bow  automatically  ad- 
justs itself  for  forward  and  backward  movements  which  feature  is 
very  important  for  shunting.  The  bow  is  probably  the  best  cur- 


FIG.  24. —  SLIDING  SHOE  OP 

BBOWN,  BOVERI  &  CO.  ^  M 

rent  collector  devised  for  high  speeds,  in  which  Case  it  may  be  as 
light  and  elastic  as  possible;  the  pressure  on  the  wire  should  not 
exceed  2  to  4  kg,  and  several  springs  acting  after  each  other  must 
neutralize  shocks  and  prevent  the  interruption  of  the  contact  by 
the  bow.  The  wind  pressure  must  be  compensated  by  wings.  The 
satisfactory  result  of  the  current  collection  on  the  experimental9 
Siemens  high  speed  car  at  10,000  volts  and  100  amp.  per  wire 
is  due  to  the  lateral  sliding  of  the  bow  (Fig.  2510),  avoiding  thereby 
the  movements  due  to  the  deflection  of  the  wire,  to  the  great  elas- 
ticity produced  by  three  consecutive  springs  and  to  the  small  weight 
of  the  cross-bar  of  the  bow  (650  grammes)  and  to  the  very  small 
pressure  of  only  2J  to  3  kg;  on  three-phase  lines  one  may  apply 
either  two  separate  bows  beside  or  behind  each  other  or  one  bow 
the  cross-bar  of  which  consists  of  two  insulated  pieces  (Brown, 
Boven  &  Company)  (Fig.  26). 

3.  Most  of  the  good  qualities  of  the  bow  are  also  to  be  found  in 
the  new  original  current  collector  of  the  MachinenfdbriJc  Oerlikon 
(Fig.  27)  consisting  of  a  curved  rod  of  brass  tubing  sliding  on  the 
lateral  overhead  wire  from  above,  when  running  on  the  free  line. 
At  stations  and  in  tunnels,  or  wherever  it  is  desired,  the  rod 
makes  contact  from  below  exactly  as  the  bow.  The  turning  of 
the  rod  through  an  angle  of  nearly  270  deg.  is  effectuated  either 
by  hand  or  pneumatically.  There  are  2X2  rods  on  each  loco- 
motive, which  may  collect  the  current  from  either  of  the  two  wires 
on  each  side  of  the  line.  In  this  way  one  wire  may  be  repaired, 

9.  The  treble  bow  is  of  course  much  too  cumbersome  to  suit  for  regu- 
lar service. 

10.  Consisting  of  a  brass  tube  with  aluminum  filling. 


NIETHAMMER:     ELECTRIC    TRACTION. 


159 


while  the  other  is  working.  The  repairs  of  the  wire  and  of  the 
current  collector  are  quickly  made  and  do  not  necessitate  the  use 
of  a  turret  car  which  blocks  up  the  line.  Without  any  serious 
sparking,  the  rod  collects  full  current  while  the  locomotive  travels 
at  full  speed  from  a  section  with  15,000  volts  to  a  line  section 
which  is  interrupted  by  the  semaphore 


FIG.  27. —  OEBLIKON  CUBEENT  COLLECTOB. 

4.  The  cylindrical  roller  collector  somewhat  resembles  the  one 
of  the  bow  type,  the  cross-bar  consisting,  however,  of  a  rotating 
roller  usually  running  on  ball  bearings.  On  the  Valtellina  loco- 
motives this  roller  for  3000  volts  and  200  amp.  per  wire  makes 
4000  revolutions  a  minute  and  consists  of  two  copper  tubes  or  two 
steel  tubes  electrolytically  covered  with  copper,  insulated  from  each 
other  by  impregnated .  wood.  The  tubes  have  to  be  replaced  after 
a  service  of  about  15,000  train-km.  There  is  one  roller  collector 
for  forward  running  and  one  for  backward  movement  (Fig.  20), 


13 


24  85 

-  M  ^s&j  MV...  45 


-<    ~    2- -  « 3—  4 

FIG.  28. —  GANZ  &  co.  TEOLLEY  SUSPENSION. 

each  being  controlled  by  compressed  air.  The  roller  is  usually 
heavier  and  less  elastic  than  the  bow.  To  avoid  the  hammering 
effect  of  the  deflection  of  the  wire,  Ganz  &  Company  propose  to  use 
two  trolley  wires  (Fig.  28)  which  cross  each  other,  the  support  of 
one  wire  being  at  the  spot  where  the  other  has  the  deepest  deflec- 
tion. 


100 


NIETHAMMER:     ELECTRIC    TRACTION. 


Overhead  wires  should  not  be  fastened  rigidly  but  In  an  elastic 
manner,  to  avoid  break-downs  of  the  wires  by  the  hammering 
effect  of  the  collector,  which  effect  increases  with  the  speed.  The 
Union  Company  fastens  the  trolley  wire  for  their  single-phase  lines 


FIG.  29. —  UNION  co.  TROLLEY  SUSPENSION. 

to  a  special  suspension  wire,  at  distances  of  3  to  4  metres,  by  vertical 
wires  of  variable  length,  obtaining  an  almost  straight  trolley  wire 
with  unnoticeable  deflection  (Figs.  29,  30  and  31).  For  voltages 
above  1000  double  insulation  of  the  trolley  wire  is  to  recommended. 
5.  From  the  third  rail  the  sliding  shoe  which  is  usually  pressed 
on  the  rail  from  above  by  its  own  weight,  or  by  springs  or  pneu- 
matically from  the  side  or  from  below,  may  collect  currents  of 


FIG.  30. —  TEOLLEY  SUSPENSION. 

more  than  2000  amp.  For  heavy  currents  this  is  the  cheapest  and 
most  durable  scheme  yet  proposed,  though  for  alternate  currents, 
the  increase  of  the  resistance  by  skin  effect  is  very  objectionable. 
The  main  difficulty  which  makes  the  third  rail  prohibitive  for 


NIETHAMMER:     ELECTRIC    TRACTION. 


161 


three-phase  lines  is  the  necessity  for  the  thorough  protection  of 
the  live  rail,  mainly  at  stations.  It  is,  however,  possible  to  cover 
the  third  rail  at  stations  by  wcoden  boards  leaving  only  a  narrow 
crevice  for  connection  with  the  shoe  (Baltimore  &  Ohio  Ky) .  If 
the  shoe  projects  laterally  from  the  car,  the  third  rail  may  easily 
be  protected  by  overhanging  boards  in  such  a  way  as  to  eliminate 
danger  to  operators  and  officials  when  crossing  the  rails.  Too 
much  protecting,  however,  prevents  rapid  inspection.  On  the 
Fribourg-Murten  line  (Switzerland)  the  third  rail  was  allowed  only 
for  the  free  line,  at  the  stations  two  bows  and  two  overhead  wires 
were  prescribed,  complicating  the  system  materially.  During  the 
erection  of  the  third  rail,  special  care  must  be  taken  to  allow  for 
heat  extension  and  to  prevent  the  movement  of  the  rail.  Overhead 


FIG.  31. —  TROLLEY  SUSPENSION. 

conductors  for  heavy  currents  above  500  amps,  would  necessitate 
very  expensive  framework  and  a  conductor  having  the  shape  either 
of  a  usual  rail  or  of  a  U  iron  or  two  Z  irons.  The  elevated  railway 
of  Elberfeld  is  using  such  an  overhead  rail  and  the  Baltimore  & 
Ohio  Ey.  formerly  used  an  overhead  tube  which,  however,  has  been 
discarded. 

If  the  same  car  has  to  run  on  tracks  with  different  voltages, 
two  different  kinds  of  current  collectors  must  be  provided.  On  the 
line  already  mentioned  with  400  and  2700  volts  single-phase,  the 
Austrian  Union  Company  has  installed  a  high  bow  for  high  tension 
and  a  low  bow  for  low  tension.  The  trolley  wire  at  the  end  of  the 
low  voltage  track  is  gradually  raised  and  the  low  bow  automatically 

leaves  the  trolley  wire. 

"ELEC.  RYS. —  11.. 


1G2  NIETHAMMER:     ELECTRIC    TRACTION. 

Disagreeable  disturbances  are  caused  on  trolley  wires  and  third 
rails  by  ice  and  sleet.  A  mechanical  remedy  consists  in  using 
scrapers  and  metal  brushes  which,  however,  deteriorate  the  con- 
ductor; it  is  also  not  always  sufficiently  effective.  On  heavy  third 
rails  may  be  applied  certain  chemicals,  as  calcium  chloride,  as  they 
readily  melt  all  ice  and  sleet,  the  soft  mass  being  easily  swept  away 
by  brushes  on  the  motor  car.  Electric  heating,  though  somewhat 
expensive,  has  also  proved  a  success,  as  on  the  Burgdorf  Thun  rail- 
way. The  line  is  short-circuited  with  low  voltage  only  as  long  as 
is  necessary  to  soften  the  ice ;  the  sliding  bow  sweeps  it  away  after- 
ward. A  thin  coat  of  varnish  on  the  trolley  wire  may  prevent 
the  formation  of  ice  without  disturbing  the  collection  of  current. 
It  is  noteworthy  that  ice  not  only  depends  from  the  lower  side  of 
the  wire,  but  it  forms  on  the  upper  side  also. 

In  overhead  switches  of  three-phase  lines  either  both  wires  or 
at  least  one  must  be  entirely  omitted  and  replaced  by  insulated 
pieces,  to  avoid  crossings  of  conductors  of  different  phases  (Fig. 


FIG.  32. —  OVERHEAD  SWITCH. 

32,  of  Brown,  Boveri  &  die).  One  should,  therefore,  always  pro- 
vide at  least  two  current  collectors  on  the  motor  cars,  spacing 
them  at  a  distance  somewhat  greater  than  the  length  of  the  over- 
head switch.  It  is  bad  practice  to  be  compelled  to  pass  all  switches 
without  current,  as  it  necessitates  special  attention  on  the  part  of 
the  motorman  and  means  low  acceleration  and  very  inconvenient 
shunting.  It  is  advantageous  to  have  at  least  one  phase  running 
all  through  the  switches  (Fig.  32),  as  in  this  case  the  motors  con- 
tinue to  work  as  single-phase  machines;  starting  is,  of  course,  ex- 
cluded. On  third-rail  tracks  there  occur  similar  interruptions 
along  street  crossings ;  at  least  two  sets  of  shoes  are,  therefore,  neces- 
sary at  each  end  of  the  car.  The  intersecting  roads  should  cross  at  a 
small  angle,  and  the  third  rail  should  continue  on  different  sides 
of  the  line  beyond  the  crossing. 

The  following  characteristic  features  seem  desirable  in  a  cur- 
rent collector  for  universal  use:     Running  and  shunting  in  both 


XlETUAUUElt:     ELECTRIC    TRACTION.  103 

directions  must  be  possible  without  reversing  the  position  of  the 
collector.  There  must  be  neither  hammering  of  wire  nor  breaking 
of  contact  at  high  speed.  The  current  collector  must  not  be  able 
to  destroy  the  line  construction  and  must  be  incapable  of  being  de- 
railed during  service.  Eepairs  of  the  collector  and  of  the  line  must 
be  quickly  made  without  interrupting  the  regular  service.  This  ne- 
cessitates either  the  simple  direct-current  system  for  volt  ages  less  thr- 
1000,  or  for  high  voltage  single-phase  railways  two  separate  trolley 
lino*  have  to  be  erected  on  both  sides  of  the  line  (Maschinenfabrik 
Oerlikon).  Simplicity  of  the  line  and  of  the  switches  which  must 
be  crossed  with  full  current  on  dictates  the  use  of  only  one  current- 
collecting  conductor.  High  voltages  from  3000  upwards  seem  ab- 
solutely necessary  for  long  lines. 

Central  Stations  and  Sub-stations. 

The  generators  and  transformers  for  single  and  polyphase 
railways  must  be  designed  for  the  apparent  input  of  the  railway 
motors,  that  is,  for  the  kilovoltamperes  which  are  considerably 
higher  than  the  kilowatts.  The  low  power  factor  of  the  current 
entails  a  much  higher  voltage  drop  than  current  at  unity  power 
factor,  which  feature  is  specially  bad  for  alternate-current  motors 
so  sensitive  to  voltage  variations.  The  mean  power  factor  on  three- 
phase  lines  is  sometimes  as  low  as  50  per  cent,  and  during  starting  it 
is  even  lower  for  single-phase  motors.  Single-phase  generators  and 
transformers  are  larger  and  more  expensive  than  those  of  the 
polyphase  type.  It  is,  of  course,  possible,  or  even  necessary,  to 
use  two-phase  generators  for  single-phase  lines,  but  both  phases  will 
always  be  far  from  equally  loaded.  Generators  and  sub-stations 
must  be  able  for  moments  to  deliver  the  maximum  output,  which 
in  some  cases  may  be  more  than  10  times  the  mean  value  on  long 
lines  with  light  traffic,  but  which  in  other  cases  may  fall  down  to 
only  50  per  cent  above  the  mean  value.  If  in  the  sub-stations  of 
direct- current  railways  storage  batteries  are  provided,  the  converters 
and  generators  may  be  very  much  reduced  in  size  and  price,  having 
to  yie<ld  only  mean  values.  Storage  batteries  are,  however,  expensive 
in  first  cost  and  in  service,  and  their  efficiency  is  only  about  75  per 
cent,  but  they  decidedly  increase  the  reliability  of  the  service  and  in 
most  cases  reduce  the  first  cost  of  the  plant  and  materially  diminish 
the  operating  expenses.  In  three-phase  or  single-phase  plants  stor- 
age batteries  would  be  possible  only  by  installing  rotaries  which 


104  NIETHAMMER:     ELECT  tUG    TRACTION. 

would  have  to  work  alternately  as  direct  and  as  inverted  con- 
verters, a  very  complicated  scheme.  By  using  very  heavy  fly- 
wheels and  a  great  speed  variation  of  the  prime  movers  between 
no  load  and  full  load,  the  power  rushes  may  be  kept  away  from  the 
prime  movers  but  not  from  the  electric  generators  and  transformers. 
The  dropping  of  the  speed  in  the  central  station  when  trains  are 
started  is  quite  favorable  to  alternating  currents,  as  the  periodicity 
is  reduced  thereby.  A  somewhat  better  scheme  would  be  the  use 
of  high  speed  fly-wheel  sets,  electrically  driven  and  influenced  by 
the  load  in  such  a  way  as  to  be  charged  in  the  shape  of  kinetic 
energy,  when  the  line  runs  at  light  loads,  and  discharged  when 
much  energy  is  needed  on  the  line.  Such  sets  must  have  a  wide 
range  of  speed  variation;  but  up  to  the  present  they  have  been 
successfully  built  only  for  direct-current  net-works. 

As  long  as  direct-current  pressures  have  to  be  kept  lower  than 
1000  volts,  the  most  serious  drawback  to  direct-current  equipments, 
besides  the  expensive  feeders  and  trolley  lines,  is  the  large  sub-sta- 
tions with  rotating  machinery.  These  latter  cost  more  for  in- 
stallation and  maintenance  than  stationary  transformers  of  the 
self -cooled  oil  type,  which  type  is  best  for  railway  service  up  to 
500  k.  v.  a.,  as  they  easily  give  4  to  5  times  the  normal  output  for 
a  short  period,  if  the  normal  maximum  voltage  drop  is  not  higher 
than  1-J  to  2  per  cent.  Rotaries  for  low  periodicities  (10  to  25)  with  a 
good  reactance  voltage  or  provided  with  auxiliary  commutation  poles 
should  stand  a  momentary  overload  of  100  to  200  per  cent.  But,  as 
a  matter  of  fact,  there  are  many  cases  in  which  even  for  long  lines 
direct-current  railways  are  not  much  more  expensive  in  first  cost 
than  single  or  three-phase  equipments,  and  the  operating  expenses 
are  very  often  in  favor  of  direct-current,  the  substations  amounting 
only  to  about  15  per  cent  of  the  price  of  the  whole  pi  ant.  By  in- 
creasing the  direct-current  voltage  or  by  the  invention  of  reliable 
stationary  converters  for  transforming  three-phase  into  direct  cur- 
rent, the  conditions  would  even  become  more  favorable  to  direct 
current. 

As  the  voltage  drop  influences  considerably  the  torque  of  all 
alternate-current  motors  the  generators  and  transformers  must  be  so 
designed  as  to  give  a  very  good  voltage  regulation  at  inductive  loads. 
The  Valtellina  generators  yield  a  short-circuit  current  six  times 
the  normal  current  with  full  load  excitation  and  are  guaranteed  to 
stand  that  current  for  two  minutes.  Compound  generators  or  oven 
those  of  the  overcom pounded  type  would  be  very  desirable  for  single 


NIETHAMMER:     ELECTRIC    TRACTION.  1G5 

and  three-phase  lines,  but  there  is  no  satisfactory  and  reliable  type 
on  the  market;  all  of  the  known  compensated  generators  are  com- 
plicated and  are  surely  not  able  to  successfully  withstand  the 
severe  conditions  of  railway  service.  There  are,  however,  excellent 
automatic  voltage  regulators  on  the  market,  which  work  nearly 
instantaneously,  and  which  seem  to  be  well  adapted  for  railway 
plants  (Tirril  regulator  of  the  G.  E.  Company  and  the  Thury  regu- 
lator of  the  Cie  de  1'Industrie  El.  Geneva). 

For  equal  trolley  voltage  and  equal  voltage  drop,  the  sub-stations 
must  be  closer  together  for  alternate  than  for  direct-current 
equipments.  For  a  dense  traffic  and  direct-current  voltages  above 
1000  it  is  often  better  practice  to  use  exclusively  central  stations, 
eliminating  the  expensive  sub-stations.  On  main  lines  the  trans- 
mission voltage  ought  to  be  as  high  as  possible,  60,000  volts  accord- 
ing to  the  present  development  of  the  art,  to  get  a  uniform  load. 
The  trolley  voltage  of  3000  to  8000  may  be  transformed  in  sub- 
stations at  distances  of  30  to  60  Ion  which  may  be  increased  to  100 
or  150  km  for  15,000  volts.  For  the  production  of  high  voltage 
direct  current  at  1500  to  4000  volts,  low  speed  generators  must  be 
used,  preferably  two  or  more  in  series,  or  machines  of  the  double 
commutator  type  may  be  employed.  These  arrangements  facilitate 
also  the  connection  of  the  neutral  wire  for  a  three-wire  net-work. 
Ilotaries  for  voltages  above  1000  should  be  fed  by  alternate  cur- 
rents of  low  periodicity,  say  10  to  15;  double  commutators  and 
auxiliary  commutating  poles  may  be  desirable. 

Years  ago  direct  current  was  declared  entirely  unsuitable  for 
long  lines  and  heavy  traffic;  today  many  give  up  three-phase  and 
direct  current  to  use  only  single-phase  of  which  we  know  very  little 
as  yet,  from  a  practical  standpoint.  I  believe  that  all  three 
systems  may  counterbalance  each  other;  yet  each  of  them  lacks  some 
desirable  features.  Direct  current  is  restricted  to  low  train  volt- 
ages and  needs  expensive  sub-stations;  three-phase  railways  make 
two  trolley  wires  necessary,  are  very  sensitive  to  voltage  variations 
and  badly  overload  the  central  stations ;  the  last  two  disadvantages 
are  more  or  less  applicable  also  to  single-phase  lines,  which  possess 
the  additional  troubles  on  the  commutator  and  the  low  efficiency. 
None  of  the  systems  offers  the  possibility  of  running  through  parts 
of  the  line  independently  of  an  outside  current  source.  Up  to  the 
present  neither  of  the  other  systems  is  known  to  be  as  reliable  and 
safe  as  the  direct  current.  The  first  costs  of  the  car  equipments 
are  throughout  higher  for  three  and  single-phase  than  for  dirort 


166  XIETHAMMER:     ELECTRIC    TRACTION. 

current ;  for  equal  voltage  the  line  equipment  is  cheapest  for  direct 
current ;  but  the  possibility  of  using  high  trolley  voltages  for  alter- 
nate currents  shifts  the  result  essentially  in  favor  of  single  and 
three-phase  currents,  mainly  of  the  former.  The  sub-stations  are 
more  expensive  for  direct  current,  while  the  central  station  costs 
least  for  direct  current.  As  to  the  operating  expenses,  the  cost 
of  attendance  for  the  sub-stations  is  unfavorable  to  direct  current. 
The  result  of  serious  comparisons  between  the  systems  shows  usually 
a  difference  in  first  cost  of  not  over  10  to  25  per  cent  and  the  differ- 
once  in  operating  expenses  is  even  less  and  in  many  cases  the  re- 
sults are  in  favor  of  direct  current.  Between  three-phase  and  single- 
phase  there  is  no  essential  difference  as  to  price,  single-phase 
having  the  advantage  of  simplicity  and  the  possibility  of  higher 
trolley  voltage,  but  possesses  the  disadvantage  of  needing  a  com- 
mutator. 

For  long  lines  and  heavy  trains  with  low  accelerations,  three- 
phase  equipments  will  always  have  good  chances,  especially  if 
through  trains  are  arranged  and  all  shunting  is  done  by  special 
engines.  On  urban  and  suburban  lines,  direct  current  is  entirely 
sufficient  and  satisfactory,  though  a  reliable  single-phase  motor 
will  be  a  hard  competitor,  as  single-phase  equipments  may  be 
arranged  to  suit  long  and  short  lines  at  the  same  time. 

Hundreds  of  thousands  of  motor  cars  with  direct-current  equip- 
ments, at  voltages  from  500  to  1000,  manufactured  by  all  impor- 
tant electric  concerns  of  the  world,  at  the  head  of  which  the  General 
Electric  Company,  Schenectady,  must  be  mentioned,  have  been  for 
many  years  in  regular  and  highly  successful  service  on  street  rail- 
ways, on  elevated  and  underground  railways,  on  mountain  railways, 
on  suburban  and  interurban  lines,  with  heavy  and  light  traffic,  with 
low  and  high  speeds.  Most  of  them  with  motor  outputs  from  20 
to  300  horse-power  have  also  proved  to  be  a  decided  financial  success. 
But  even  the  heaviest  locomotives  of  the  world  with  pretty  hign 
speeds  will  successfully  operate  with  direct-current  equipments  at 
750  volts,  I  mean  the  New  York  Central  engines  of  2200  horse- 
power and  the  hauling  locomotives  of  2  X  1000  horse-power  of  the 
Baltimore  &  Ohio  Ey.  for  1600-ton  trains.  There  is  also  a  high 
voltage  direct-current  line  in  regular  service  in  France  built  by 
Thury  at  2  X  1200  volts  and  with  4  motors  of  125  horse-power  per 
locomotive. 

Three-phase  equipments  have  been  adopted  on  two  or  three  street 
railways,  on  several  mountain  railways  and  on  two  main  lines,  viz., 


X  LET  HAMMER:     ELECTRIC    TRACTION.  167 

i.he  Burgaorf  Thun  line  (Brown,  Boveri  &  Company)  with  200  to 
300  horse-power  per  train,  speeds  up  to  36  km  and  accelerations  of 
0.24  in  (per  sec.)2  besides  that  on  the  Valtellina  Kailway  in  Italy 
where  locomotives  are  running  now  with  1200  horse-power  and 
speeds  up  to  64  km  with  accelerations  of  0.16  m  (per  sec.).2  Besides 
the  experimental  work  on  the  Berlin  Zossen  line,  all  the  three-phase 
railways  are  due  to  Brown,  Boveri  &  Cie  and  Ganz  &  Company.  The 
last  concern  has  orders  for  two  more  three-phase  lines  in  Canada 
and  in  England  with  1000  and  600  volts  at  the  trolley  wire  and  loco- 
.notives  of  about  200  horse-power. 

There  are  only  a  few  single-phase  railways  in  service  as  yet. 
There  is  the  short  track  on  a  suburban  line  of  Berlin  (Spindler- 
felde)  equipped  by  the  Union  Company  with  motor  cars  having  four 
motors  of  120  horse-power  each,  6000  volts  at  the  train  and  pretty 
high  acceleration.  Moreover  there  is  the  Stubaithalbahn  in  Austria, 
a  tourist  line  with  light  traffic,  also  equipped  by  the  Union  Company 
with  motor  cars  having  two  motors  of  50  horse-power  each  and  2700 
volts  on  the  trolley.  Another  line  equipped  by  the  same  concern 
with  similar  cars  will  operate  in  Belgium  (Borinage).  The  Sie- 
mens-Schuckert  Werke  are  building  the  Oberammergau  Railway  in 
in  Bavaria,  a  short,  steep  line  with  light  traffic,  and  the  Westing- 
house  Company  has  two  interurban  lines  of  over  250  km  total 
length  under  construction  (Fort  Wayne  and  Indianapolis).  Many 
single-phase  projects  and  tenders  have  been  worked  out  and  offered, 
mainly  for  urban,  suburban  and  interurban  lines,  with  motors  from 
30  to  150  horse-power,  and  the  Union  Company  goes  even  as  high 
as  300  horse-power.  Thus  it  may  be  expected  that  the  next  few 
months  and  years  may  tell  us  many  a  practical  tale  and  may  prove 
to  be  markstones  in  the  development  of  long  distance  and  heavy 
electric  railways. 


1.08  NIETHAMMER:     ELECTRIC    TRACTION. 

APPENDIX. 

While  this  paper  is  being  printed,  various  facts,  mainly  relating 
to  single-phase  traction,  have  become  known  which  should  be  men- 
tioned here.  Besides  the  various  heavy  three-phase  locomotives 
with  motors  in  concatenation  and  with  variable  number  of  poles, 
there  has  been  placed  an  order  to  equip  a  locomotive  with  four 
single-phase  commutator  motors  of  the  Finzi  type,  each  motor  for 
100  horse-power  at  15  cycles  and  300  volts. 

Speaking  of  starters,  I  mentioned  that  Brown  and  Boveri  are 
perfecting  a  single-phase  system  using  the  repulsion  motor  and 
doing  all  regulation  by  brush  shifting.  This  scheme,  proposed  by 
Max  Deri,  is  described  in  the  Swiss  patent  28964.  The  motor  has 
two  systems  of  brushes,  and  for  a  bipolar  motor  four  brush  sets. 
One  system  has  its  axis  coinciding  with  that  of  the  stator  field ;  the 
other  system  is  shifted  by  an  angle  which  is  nearly  zero  at  standstill 
and  is  increased  corresponding  to  torque  and  speed.  Both  systems 
may  be  shifted,  one  alternately  remaining  in  the  field  axis ;  starting, 
regulating  and  braking  being  effectuated  in  this  simple  way.  One 
brush  set  of  one  system  is  directly  connected  with  the  nearest  set 
of  the  other  system. 

The  Lahmeyer  Company  of  Frankfort  is  also  developing  a  com- 
pensated repulsion-motor  for  railway  purposes.  On  the  commu- 
tator, supposed  bipolar,  there  are  four  brush  sets  90  degrees  apart 
from  each  other.  The  first  and  second  brush  set  is  interconnected 
by  a  short-circuit  and  the  third  and  fourth  as  well.  The  connecting 
points  are  closed  on  the  secondary  winding  of  a  regulating  trans- 
former whose  primary  is  fed  by  the  line  in  multiple  with  the  field 
winding,  the  secondary  windings  having  a  series  of  taps.  The 
working  conditions  are  similar  to  those  of  the  compensated  motor 
Fig.  7. 

In  a  great  many  cases  alternating-current  lines  will  be  extensions 
of  existing  direct-current  networks,  giving  rise  to  these  two  im- 
portant conditions: 

1.  The  alternating-current  motors  must  be  fed  from  the  existing 
high-tension  three-phase  transmission  line  at  25  cycles.  As  to  this 
point,  there  is  no  difficulty  either  for  three-phase  or  for  single- 
phase  car  equipments ;  in  the  last  case  it  is  advisable  to  transform 
the  three-phase  into  two-phase  currents  by  conveniently  connecting 
up  the  line  transformers,  and  to  feed  the  trolley  line  sections 
alternately  by  the  two  phases. 


NIETHAMMER:     ELECTRIC    TRACTION.  109 

2.  The  more  difficult  condition  is  to  equip  line  and  cars  in  such 
a  way  that  all  vehicles  may  be  equally  well  fed  hy  high-tension 
alternating  current  and  direct  current.  The  fulfillment  of  this 
condition  is  the  most  characteristic  feature  of  the  recently-opened 
Schenectady  extension  line  of  the  General  Electric  Company,  which 
I  need  not  to  describe  in  detail  here.  It  is  interesting  that  this 
company  with  the  widest  and  most  thorough  experience  in  electric 
traction  has  given  up  the  repulsion  motor  to  use  the  series  motor 
with  a  distributed  compensating  winding  shifted  by  half  a  pole- 
pitch  against  the  main  field  winding  and  in  series  with  the  main 
current.  This  auxiliary  winding  resembles  the  well-known  Evan 
winding  of  direct-current  machines,  neutralizing,  as  far  as  I  see, 
the  armature  cross  ampere-turns  as  well  as  the  reactance  voltage  of 
the  short-circuited  coils.  The  motor  has  no  projecting  poles  but  a 
two-phase  winding  equally  distributed  in  slots.  Both  the  600  volts 
direct  current  and  the  2200  volts  alternate  current  are  collected  by 
trolley  wheels,  the  high-tension  by  a  lateral  trolley,  both  trolley 
wires  being  on  the  same  poles.  The  50-hp  motors  for  200  volts 
across  terminals  seem  to  have  an  air-gap  of  2  mm  or  more.  The 
step-down  transformer,  which  is  not  used  for  regulation,  is  cooled 
by  air  draught.  The  total  motor  efficiency  as  a  single-phase  motor 
is  smaller  by  5  per  cent  than  in  direct-current  working;  the  power 
factor  is  90  to  95  per  cent.  The  kilo  volt-amperes  input  for  a 
complete  run  on  the  suburban  line  are  nearly  50  per  cent  higher 
for  alternating  current  than  for  direct  current.  Starting  and 
regulation  are  effectuated  for  both  currents  by  the  same  series- 
parallel  control  using  the  same  five  resistances  and  the  same  con- 
troller, the  efficiency  of  acceleration  being  somewhat  smaller  than 
for  voltage  control. 

Ganz  &  Company  are  just  building  a  three-phase  line  in  Canada 
where,  as  I  am  informed,  the  same  condition  has  to  be  fulfilled, 
viz.,  the  same  cars  have  to  run  on  three-phase  and  direct-current 
lines.  Probably  the  motors  are  equipped  with  three  slip-rings  and 
a  commutator  on  the  same  rotor  shaft,  both  being  connected  to  the 
same  armature  winding;  the  three-phase  voltage  is  reduced  to  the 
corresponding  value  by  transformers  and  fed  to  the  slip-rings,  the 
stator  serving  as  field  for  the  direct-current  service  and  as  induced 
secondary  for  the  three-phase  work.  For  both  services  the  same 
liquid  starter  may  be  used.  The  stator  winding  should  preferably 
be  two-phase. 


170  XIETHAMMER:     ELECTRIC    TRACTION. 

The  Oerlikon  Company  has  published  data  on  a  single-phase 
series  motor  of  200  horse-power,  650  r.  p.  m.,  15  periods  and  250 
volts.  It  has  eight  projecting  poles;  between  them  eight  smaller 
commutating  poles  excited  by  the  main  current  are  arranged, 
neutralizing  the  cross-field  and  the  reactance  voltage.  High  iron 
inductions  and  equalizers  for  the  multiple  armature  winding  are 
used.  The  motor  may  just  as  well  be  worked  by  direct  current. 

DISCUSSION. 

CHAIRMAN  DUNCAN:  General  discussion  on  the  subject  of  the  fore- 
going papers  is  now  open. 

Mr.  E.  KILBURN  SCOTT  :  The  advocacy  of  single-phase  as  opposed  to 
three-phase  systems  always  strikes  me  in  this  way  —  if  you  ask  a  man 
to  build  an  engine  with  a  uniform  turning  movement,  he  will  supply  you 
with  a  three-crank  engine,  and  if  you  use  only  one  of  the  cylinders,  that 
is,  only  one  line  of  parts,  you  will  be  considered  more  or  less  incompetent. 
Now,  every  three-phase  generator,  and  every  induction  motor  is  analogous 
to  the  three-crank  engine,  and  if  used  single-phase  only,  it  is  roughly 
equivalent  to  using  the  single  crank. 

One  point  which  strikes  me  as  being  very  favorable  to  three-phase,  is 
that  if  you  have  the  transformers  connected  in  delta,  and  one  of  them 
breaks  down,  the  other  two  carry  the  load.  On  the  other  hand,  in  a 
single-phase  transmission  and  distribution,  for  whatever  purpose,  if  the 
transformer  breaks  down,  the  circuit  is  opened. 

Regarding  the  question  of  the  utilization  of  alternating  currents  for 
power  —  if  single- phase  is  being  used,  the  magnetic  field  and,  therefore, 
the  torque  pulsates  with  each  alteration,  whereas  with  three-phase,  as 
with  direct  currents,  the  torque  and,  therefore,  the  draw-bar  pull  is 
steady. 

Assume  for  a  moment  a  locomotive  for  a  freight  train  and  suppose  a 
draw-bar  pull  of  ten  tons  is  required.  In  steam  locomotive  practice,  the 
locomotive  will  weigh  about  five  times  the  amount  of  the  draw-bar  pull; 
or,  say,  fifty  tons.  With  direct-current  motors  as  with  three-phase  motors, 
the  locomotive  will  also  weigh  say  fifty  tons,  since  it  has  a  constant 
torque;  but  with  single-phase  motors,  because  the  torque  is  variable,  it 
must  weigh  eighty-five,  or  perhaps  one  hundred  tons,  depending  on  the 
character  of  the  particular  motor  used.  I  do  not  want  to  go  further  at 
this  time  into  the  alternating-current  problem,  as  applied  to  traction; 
but  the  above  three  points,  are,  I  think,  pertinent  to  the  discussion  on 
Mr.  Lincoln's  paper. 

Mr.  B.  G.  LAMME:  In  dealing  with  the  problem  of  single-phase  railway 
motors  with  electrical  engineers  during  the  past  two  or  three  years, 
I  have  found  that  their  opinions  are  based  largely  on  such  experience 
as  they  have  had  with  other  types  of  alternating-current  motors.  They 
apparently  make  no  distinction  between  one  type  of  alternating  motor 
and  another,  and  there  have  been  a  number  of  points  brought  up  regarding 
which  I  find  there  is  considerable  confusion  in  their  minds.  One  of 
these  points,  mentioned  in  Mr.  Steinmetz'  paper,  is  that  of  the  large 


NIETHAMMER:     ELECTRIC    TRACTION.  171 

air-gap  permissible  with  the  single-phase  commutator-type  motor.  I  find 
that  a  great  many  engineers  cannot  understand  why  a  single-phase  com- 
mutator-type motor  can  have  a  larger  air-gap  than  an  induction  motor 
of  the  same  speed  and  capacity,  and  still  have  a  higher  power  factor. 
I  have  explained  this  point  in  a  non-mathematical  way  which  seemed 
to  be  satisfactory  to  them,  and  which  they  can  check  for  themselves  if 
they  so  desire.  This  explanation  is  as  follows: 

Take  a  polyphase  motor  of  any  of  the  well-known  types,  but  preferably 
of  the  collector-ring  type,  for  convenience.  Run  the  machine  at  full  speed, 
and  note  the  no-load  current  or  magnetizing  current.  Then  open  one  cir- 
cuit; so  that  the  primary  or  field  of  the  motor  is  operated  on  single- 
phase,  and  it  will  be  noted  that  the  motor  takes  practically  the  same 
total  apparent  input  as  before.  This  is,  if  it  is  a  two-phase  motor,  for  ex- 
ample, and  one-phase  is  opened,  the  remaining  phase  takes  twice  as  much 
current  as  before.  Therefore,  as  regards  total  amount  of  magnetizing 
current  required,  it  apparently  makes  no  difference  whether  the  induc- 
tion motor  is  operated  polyphase  or  single-phase. 

Next,  if  the  secondary  circuit  of  the  motor  is  opened,  the  motor  still 
being  run  at  full  speed,  it  will  be  noted  that  with  all  phases  connected, 
the  magnetizing  current  supplied  the  motor  remains  as  before;  but  with 
only  one-phase  on  the  primary,  the  total  magnetizing  current  of  the  motor 
drops  to  one-half,  while  with  the  secondary  closed,  the  total  current  was 
the  same  for  either  single-phase  or  polyphase.  This  indicates  at  once 
that  with  the  secondary  closed  the  large  magnetizing  current  with  one- 
phase  on  the  primary  is  a  direct  result  of  the  closed  or  short-circuited 
secondary,  for  closing  the  secondary  winding  on  itself  at  once  doubles  the 
total  magnetizing  current  of  the  single-phase  primary.  Any  armature 
which  has  a  winding  not  short-circuited  on  itself  will,  when  placed  in  this 
primary,  have  the  same  effect  as  the  open  secondary  in  the  above  illustra- 
tion. An  armature  or  secondary  element,  with  a  direct-current  type  of 
winding,  has  the  same  effect  as  the  open  secondary,  as  such  a  winding  is 
not  closed  or  short-circuited  on  itself  in  the  sense  that  an  induction-motor 
secondary  winding  is  closed  on  itself.  Therefore,  it  follows  that  a  single- 
phase  motor  with  a  secondary  or  armature  with  a  direct-current  type 
of  winding  will  absorb  only  one-half  as  much  magnetizing  current  in  its 
primary  or  field,  as  would  be  taken  by  a  single-phase  motor  or  polyphase 
motor  of  the  induction  type.  It  is,  therefore,  evident  as  the  magnetizing 
current  is  only  one-half  of  that  of  the  corresponding  induction  motor,  the 
air-gap  can  be  very  much  increased  if  the  commutator-type  motor  is 
allowed  to  take  the  same  magnetizing  current  as  the  induction  type. 

A  second  point  which  I  have  found  required  considerable  explanation 
is  the  fact  that  the  series  type  of  single-phase  motor  can  give  a  very 
large  starting  torque  with  a  poor  power-factor.  Experience  of  electrical 
engineers  has  been  founded  on  induction-motor  practice,  in  which  a  low 
power-factor  at  start  means,  in  general,  rather  poor  starting  torque. 
They  consequently  believe  that  poor  power-factors  and  poor  torque  at 
start  go  together.  They  do  not  comprehend  that  there  is  one  great  differ- 
ence between  the  series  type  of  single-phase  motor  and  the  induction  motor, 
single-phase  and  polyphase,  and  that  is  that  in  the  series  type  of  motor, 


172  NIETHAMMER:     ELECTRIC    TRACTION. 

the  current  taken  by  the  motor  represents  torque  without  regard  to  the 
power-factor.  That  is,  the  magnetizing  and  other  wattless  components 
of  the  current  represent  starting  torque  just  as  well  as  the  energy  com- 
ponent. In  the  induction  motor  on  the  other  hand,  the  magnetizing  and 
other  wattless  components  of  the  current  supplied  to  the  motor  repre- 
sent no  torque,  and  it  is  only  the  energy  component  of  the  current  that 
can  represent  torque.  Therefore,  if  the  induction  motor  has  a  low  power- 
factor  at  start,  it  means  a  low  energy  component,  and,  therefore,  of  the 
total  current  supplied  but  a  small  proportion  represents  torque.  High 
torque  in  the  induction  motor  at  start  must  be  obtained  by  high  losses, 
represented  by  resistance  losses  in  the  secondary  or  armature  circuit  of 
the  motor.  On  the  other  hand  as  mentioned  above,  in  the  series  type  of 
single-phase  motor,  high  torque  at  start  does  not  mean  high  losses,  as  the 
wattless  component  assists  in  developing  torque.  Therefore,  for  rail- 
way work  where  induction-type  motors  are  used,  rheostatic  control  is 
always  used  in  order  to  obtain  high  energy  loss  at  start  for  obtaining 
the  necessary  high  starting  torque,  but  with  single-phase  railway  motors 
of  the  series  type,  it  is  only  necessary  to  get  the  required  current  through 
the  motor  for  the  desired  torque,  as  in  the  direct-current  series  motor,  and 
the  voltage  at  the  terminals  of  the  motor  can  be  adjusted  to  that  required 
to  send  the  necessary  current  through  the  motor.  Full-load  current 
through  the  motor  will  give  full -load  torque,  without  regard  to  the  voltage 
supplied,  and  if  this  full  load  current  can  be  supplied  to  the  motor  at 
much  lower  than  lull-load  voltage,  then  full-load  torque  will  be  obtained 
in  such  motors  with  much  less  than  full-load  input.  If  half  full-load 
voltage,  for  example,  is  required  to  send  full-load  current  through  the 
motor  at  start,  then  full-load  torque  will  be  obtained  with  one-half  the 
normal  input  of  the  motor,  and  furthermore  this  reduced  input  will  be 
at  a  relatively  low  power-factor.  This  lower  power-factor  at  start  would 
have  considerable  effect  on  the  transmission  system,  but  it  is  compensated 
for  by  the  reduced  input  at  start. 

In  Mr.  Steinmetz'  paper,  where  he  gives  comparisons  of  the  different 
types  of  commutator  motors,  he  refers  to  them  as  the  plain  series,  the 
directly  compensated,  and  the  induced  compensated.  My  experience  has 
been  almost  entirely  with  the  directly  compensated,  and  that  is  practically 
the  only  method  that  the  company  which  I  represent  has  been  using.  Be- 
fore the  American  Institute  last  winter,  in  a  discussion  on  this  subject, 
I  referred  to  this  type  under  a  different  term.  I  spoke  of  it  as  a  "  straight 
series  motor  ",  describing  it  as  one  with  all  the  windings  in  series.  That 
was  intended  to  distinguish  it  from  the  motor  with  the  compensating 
winding  short-circuited  on  itself.  My  experience  has  shown  that  such 
a  winding  is  not  the  equal  of  the  type  where  the  neutralizing  or  balancing 
winding  is  in  series  with  the  other  windings.  I  have  also  found  that 
the  best  results  on  the  average  are  obtained  with  the  neutralizing  winding 
just  balancing  the  armature  winding,  not  over  or  under  compensated,  and 
one  measure  for  testing  our  compensating  windings  has  been  to  put  a 
short-circuiting  connection  across  the  terminals  of  the  neutralizing  wind- 
ing. When  this  winding  is  properly  proportioned,  but  very  little  current 
will  be  obtained  through  the  short-circuiting  wire. 


NIETHAMMER:     ELECTRIC    TRACTION.  178 

Dr.  C.  P.  STEINMETZ:  In  regard  to  the  question  raised  of  the  relative 
advantages  of  single-phase  and  polyphase  motors, — the  induction  type  of  mo- 
tor —  the  single-phase  motor  tends  to  synchronize  much  more  strongly  than 
the  polyphase  motor.  That  is,  the  range  of  efficient  operation  in  the  single- 
phase  motor  is  much  more  limited,  and  by  deviating  from  synchronous 
speed,  the  torque  and  power  fall  off  very  much  more  rapidly  in  the  single- 
phase  induction  motor  then  in  the  polyphase  motor;  so  that  while  a  poly- 
phase induction  motor  could  still  be  used  for  railroad  work,  where  rapid 
and  frequent  acceleration  is  not  demanded,  the  single-phase  induction 
motor  is  out  of  the  question  for  this  work,  except  by  methods  as  Mr. 
Arnold  has  shown  us  here  so  nicely,  whereby  the  motor  is  really  not  re- 
quired to  start  and  accelerate  with  the  train.  The  reverse  condition, 
however,  is  found  with  the  commutator  motor.  Investigation  of  all  the 
very  many  different  forms  of  alternating  commutator  motors  has  shown 
me  that  the  tendency  of  the  single-phase  commutator  motor  to  cover 
efficiently  a  very  wide  range  of  speed  is  much  more  marked  than  in  the 
polyphase  commutator  motor.  This  can  well  be  understood.  In  any  motor 
the  torque  is  produced  by  the  action  of  a  magnetic  field  on  the  resultant 
current  flowing  in  the  rotor  in  quadrature  position  to  the  magnetic  field. 
In  the  polyphase  motor,  where  you  have  a  stator  polyphase  field,  the 
magnetic  flux  in  the  direction  of  the  effective  field  is  necessarily  deter- 
mined by  the  impressed  e.m.f.  and  so  limited.  In  the  single-phase  com- 
mutator motor,  however,  there  is  a  direction  in  quadrature  to  the  mag- 
netomotive force  of  the  impressed  primary  circuit,  where  no  limit  exists 
to  the  magnetic  flux,  except  magnetic  saturation,  and  in  this  direction  a 
magnetic  field  can  be  produced  which  is  not  limited  by  the  impressed 
e.m.f.,  but  varies  more  or  less  in  inverse  proportion  to  the  speed;  so  that 
such  a  single-phase  commutator  motor  can  be  made  to  give  the  character- 
istic of  the  direct-current  series  motor;  that  is,  to  give  a  torque  propor- 
tional approximately  to  the  square  of  the  current,  while  in  the  polyphase 
motor  the  tendency  is  always  in  the  direction  of  a  torque  only  propor- 
tional to  the  current.  Going  down,  then,  to  low  speeds  and  starting,  you 
find  that,  other  things  being  equal,  the  single-phase  commutator  motor 
gives  the  better  torque  efficiency  as  compared  with  the  polyphase  com- 
mutator motor,  while  the  reverse  is  the  case  with  the  induction  motor. 

As  regards  the  comparison  with  the  single-cylinder  and  multiple-cylinder 
steam  engine,  after  all  the  single-cylinder  steam  engine  when  running  is 
not  inferior  in  this  respect  to  the  three-cylinder  steam  engine,  and,  in 
fact,  even  now-a-days,  there  are  steam  engines  built  and  operated  at  the 
highest  efficiency  which  are,  as  far  at»  this  feature  is  concerned,  single- 
cylinder  engines;  that  is,  where  the  multiple  expansion  is  carried  out 
in  several  cylinders  connected  in  tandem,  where,  therefore,  you  get  the 
pulsating  torque.  The  objection  to  the  single-cylinder  characteristic  is 
that  the  frequency  of  impulses  varies  with  the  speed,  and  is  very  low  at 
low  speed  and  results  in  a  dead  point  at  stand-still.  But  this  is  not  the 
case  in  a  single-phase  motor,  where  the  frequency  of  impulses  is  constant, 
is  the  impressed  frequency  of  alternations,  and  not  the  frequency  of  speed, 
as  with  the  steam  engine,  and  is  so  high  that  the  motor  cannot  be  built  with 


174  NIETHAMMER:     ELECTRIC    TRACTION. 

as  low  momentum,  as  low  mass,  to  give  a  noticeable  variation  of  speed,  due 
to  the  successive  impulses  of  torque. 

As  regards  the  system  of  distribution,  whether  polyphase,  three-phase 
or  single-phase,  for  electric  railroading, —  for  general  distribution,  poly- 
phase systems  are  used  almost  exclusively  in  this  country.  That  is,  for 
many  years  we  have  been  impressed  and  educated  to  consider  this  as  the 
proper  thing.  I  understand  it  is  not  quite  so  abroad  Single-phase 
systems  are  still  used  there  to  a  considerable  extent.  The  polyphase 
system  has  a  decided  advantage  in  stationary  motor  work:  the 
polyphase  stationary  motor,  of  the  induction  or  synchronous  type,  is 
decidedly  superior  to  the  single-phase  motor,  and  will  remain  so,  and 
that  is  the  foremost  value  and  importance  of  the  polyphase  sys- 
tem. The  polyphase  generator  is  a  little  smaller,  a  little  more  efficient 
than  the  single-phase  generator.  I  do  not  believe,  however,  that  the  dif- 
ference in  generators  is  so  essential  as  to  throw  the  balance  in  favor  of 
the  polyphase  system.  But  it  is  in  the  motor  work.  In  every  other  re- 
spect the  single-phase  system  is  simpler  and  more  reliable,  and  even  if 
the  three-phase  system  by  the  use  of  three  transformers  connected  in  delta 
gives  the  result  that  if  any  one  of  the  transformers  burns  out,  the  other 
two  can  maintain  the  service:  in  the  single- phase  system  by  using  two 
transformers,  which  means  larger  units,  and  a  better  arrangement,  if 
one  burns  out,  the  other  one  can  maintain  the  service,  so  you  still  have 
an  advantage. 

Mr.  E.  KILBUBN  SCOTT:     It  has  to  be  switched  in. 

Dr.  STEINMETZ:  Switching,  controlling,  everything  is  simpler,  and 
more  convenient,  in  the  single-phase  system  than  in  the  polyphase  system, 
and  my  opinion  is  that  if  it  were  not  for  the  question  of  motors,  the 
polyphase  system  would  never  have  reached  its  present  standing. 

Now,  when  you  come  to  railway  work,  and  the  commutator  motor,  this 
question  changes,  and  the  advantage  of  the  polyphase  system  becomes  a 
disadvantage.  The  motor  must  be  a  single-phase  motor,  and  you  must 
run  a  single-phase  system  from  a  polyphase  generating  system.  Now  we 
can  indeed  do  that  by  distributing  the  railway  load  on  the  different 
phases,  operating  a  two-track  road  from  a  two-phase  system  by  having 
one  track  on  one-phase  and  the  other  track  on  the  other  phase,  or  cutting 
the  road  up  into  sections  and  connecting  the  sections  with  the  different 
phases.  In  railroading,  the  foremost  condition  is  absolute  reliability 
regardless  of  everything  else.  Now,  as  soon  as  you  cut  up  the  system  in 
different  phases,  where  two  tracks  are  in  different  phases,  any  switch  or 
transfer  device  from  track  to  track  leads  to  difficulties.  If  you  cut  the 
road  up  into  sections,  you  must  have  a  dead  section  between  the  two 
longer  than  the  longest  train  that  ever  will  be  run,  otherwise  you  are 
liable  to  run  the  same  train  on  the  two  different  phases,  getting  a  dead 
short-circuit.  I  think  it  is  objectionable  to  have  any  possibility  of  a 
place  on  the  road  where  a  train  may  get  stalled  and  be  unable  to  pro- 
ceed, and  I  think  these  objections  may  lead  us  again  to  consider  the 
single-phase  generator,  and  I  believe  if  the  single-phase  generator  is  taken 
up  with  the  modern  engineering  methods,  with  modern  experience  in 
design,  we  can  get  a  single-phase  generator  which,  while  probably  not 


NIETHAMMER:     ELECTRIC    TRACTION.  175 


exactly  as  small  and  efficient  as  the  three-phase,  will  nevertheless  be 
so  close  to  it,  that  it  will  fully  fill  the  requirements,  and  my  personal 
opinion  is  that  if  you  run  railroads  with  single-phase  motors,  if  there 
are  no  other  conditions  to  be  met,  the  best  way  would  be  to  generate 
your  power  single-phase  and  transmit  it  single-phase  and  operate  the 
whole  system  on  the  same  circuit  with  the  greatest  possible  simplicity, 
doing  away  as  far  as  possible  with  the  duplicating  of  transformers,  the 
duplicating  of  feeders,  the  existence  of  dead  sections  and  the  incon- 
venience in  switching  or  transfer. 

Mr.  A.  H.  ARMSTRONG:  The  adoption  of  either  three-phase  or  the  single- 
phase  generators  is  not  a  purely  engineering  question,  but  it  is  necessary 
to  consider  the  commercial  aspects  of  the  case  as  well.  There  are  probably 
operating  in  this  country  some  half  million  kw  of  rotary  converter  and 
three-phase  generating  apparatus.  The  object  of  developing  the  single- 
phase  railway  motor  along  the  lines  of  25-cycle  supply  was  that  it 
might  utilize  so  far  as  possible  this  half-million  kw  of  apparatus. 
In  advocating,  therefore,  the  single-phase  generating  and  distributing 
system,  we  are  confronted  with  the  possibility,  in  many  cases  even  the 
necessity,  of  using  the  supply  of  power  already  available.  To  meet  this 
condition,  the  company  which  I  represent  has  devised  a  scheme  of  balancing 
by  the  three-phase-two-phase  step-down  transformer  connection,  making 
each  sub-station  balanced  in  itself,  and  equally  loading  the  three  legs  of  the 
usual  three-phase  distributing  system.  By  this  means  it  is  possible  to  use 
existing  distributing  systems,  and  to  consider  the  claims  of  stationary 
motor  work  in  any  new  system  that  is  considered.  The  single-phase 
system  of  generation  and  distribution  is  of  course  the  simplest  possible 
for  railway  work.  It  approaches  more  nearly  to  the  direct-current  system 
of  distribution,  and  is  preferable,  but  many  electric  railway  installations 
have  reached  such  magnitude,  and  have  so  many  secondary  claims  upon 
them,  such  as  lighting  and  general  power  distribution,  that  the  railway 
interests  alone  cannot  be  considered  by  themselves.  Three-phase  generat- 
ing and  distributing  systems  already  exist,  and  must  be  utilized,  and 
secondary  claims  will  probably  influence  the  introduction  of  the  same  class 
of  machinery  in  the  new  plants.  Thus,  while  the  single-phase  system  is 
preferable  and  simple,  considered  from  the  engineering  standpoint  alone, 
it  is  probable  that  three-phase  distribution,  or  multiphase  distribution, 
will  have  to  be  carefully  considered  even  though  the  motors  adopted  are 
of  the  single-phase  type. 

Mr.  E.  KILBURN  SCOTT:  Mr.  Steinmetz,  will  you  tell  me  where  this 
analogy  is  wrong?  Suppose  I  go  to  a  carpenter  and  ask  him  to  make  me 
something  to  stand  upon  which  shall  have  the  minimum  quantity  of  ma- 
terial and  the  maximum  strength,  he  makes  me  a  three-legged  stool.  If 
he  should  make  it  with  four  legs,  which  is  analogous  to  two-phase,  —  well, 
it  might  stand  on  four,  but  the  chances  are  it  will  rest  on  three  only,  the 
extra  leg  in  other  words  being  so  much  wasted  work  and  material.  If  he 
should  n-,ake  it  with  two  legs,  which  I  think  is  analogous  to  single-phase, 
it  would  be  in  unstable  equilibrium. 

Mr.  STEINMETZ:  But  if  you  make  a  vehicle  with  three  wheels,  a  tri- 
cycle, you  can  never  get  the  speed  out  of  it  that  you  can  out  of  a  bicycle. 


170  NIETHAMMER:     ELECTRIC    TRACTION. 

That  is,  as  soon  as  you  get  motion  and  have  dynamic  conditions  things 
change  entirely  from  static  conditions. 

Mr.  SCOTT:    Yes,  I  see. 

CHAIRMAN  DUNCAN:  We  should  like  to  have  some  further  discussion. 
There  are  certainly  gentlemen  present  who  can  add  to  our  information  on 
the  subject.  Mr.  Leonard,  we  should  like  to  hear  something  about  Mr. 
Arnold's  locomotive.  I  know  you  have  considered  that  type. 

Mr.  H.  WARD  LEONARD:  I  believe,  Mr.  Chairman,  that  I  was  the  first 
to  urge  the  idea  that  single-phase,  high-tension  generation  and  distribu- 
tion were  essential  for  heavy  railway  work,  and  as  some  of  the  gentlemen 
present  may  not  understand  the  system  that  I  proposed,  since  it  was 
many  years  ago,  I  will  state  briefly  that  what  I  proposed  was  a  high-tension 
single-phase  system  with  a  single-phase  motor  upon  the  locomotive  running 
at  a  constant  speed,  and  driving  upon  the  locomotive  a  generator,  which 
generator  would  have  a  separately  excited  field,  by  means  of  which  the 
voltage  of  the  continuous  current  in  the  secondary  could  be  varied  as 
desired  and  reversed,  by  which  means  we  could  secure  in  the  armatures 
of  the  propelling  motors  of  the  locomotive  any  desired  voltage  to  accelerate 
from  rest  to  full  speed,  with  a  minimum  consumption  of  watts  and  with  the 
many  advantages  of  perfect  speed  control,  restoration  of  energy,  etc.  Mr. 
Arnold's  proposition  follows  similar  lines,  to  the  point  where  the  shaft 
of  the  single-phase  motor  is  reached.  From  that  point  he  uses  compressed 
air  in  conjunction  with  the  torque  of  the  single-phase  motor,  and  he 
secures  very  many  beautiful  features  and  important  ones,  although,  as  I 
believe,  at  the  expense  of  simplicity.  He  has  one  advantage  which  may 
have  considerable  weight,  although  I  believe  that  it  will  not  be  so  in- 
fluential as  to  be  of  very  great  effect,  and  that  is  the  storage  of  power 
for  the  operation  of  the  train  without  electric  current  for  a  short  dis- 
tance. But  a  system  having  reciprocating  parts  and  the  complexity  due 
to  the  necessity  of  a  good  many  valves  and  automatic  devices,  I  per- 
sonally do  not  think  is  likely  to  compare  in  reliability  of  service  with  a 
single  revolving  part  without  separate  automatic  devices  or  reciprocating 
parts.  A  point  in  connection  with  my  system  which  is  also  likely  to  be 
important,  perhaps,  is  that  although  a  high-tension  current  would  prefer- 
ably be  led  upon  the  locomotive,  it  is  led  to  a  single-phase  motor  which 
is  an  entirely  separate  device  and  can  be  entirely  insulated  at  the  shaft 
from  the  rest  of  the  locomotive,  so  that  we  reduce  to  a  minimum  the 
liability  of  the  high-tension  energy  reaching  any  portion  of  the  locomotive 
which  has  to  be  handled,  or  where  a  person  might  be  exposed  to  it. 

As  to  the  comparative  weights  and  first  cost,  it  is  difficult  to  form  a 
conclusion  with  any  of  the  data  that  we  have  at  present  at  hand  as  be- 
tween the  air-storage  scheme  and  the  transformation  at  variable  voltage, 
but  I  should  be  inclined  to  expect  that  the  first  cost  and  weight  for  my 
system  would  be  rather  less  than  for  the  other.  In  that  connection  I  was 
interested  to  notice  the  figures  which  are  given  in  Prof.  Niethammer's 
paper,  on  page  237,  where  Table  VIII.  gives  the  weights  for  the  direct- 
current,  three-phase  and  single-phase  apparatus.  Considering  the  three- 
phase  and  the  single-phase,  and.  putting  those  figures  into  the  weight  per 
horse-power  of  the  electrical  equipment  on  the  locomotive,  and  putting 


NIETHAMMER:     ELECTRIC    TRACTION.  177 

the  kilograms  roughly  into  pounds,  we  get  the  following  figures:  Three- 
phase,  Brown-Boveri,  72  Ibs.  per  h.p.;  Siemens  &  Halske,  three-phase,  89 
Ibs. ;  A.  E.  G.,  three-phase,  53  Ibs. ;  Ganz  &  Co.,  three-phase,  60  Ibs.  Single- 
phase. —  Finzi,  88  Ibs.;  Union,  73  Ibs.;  Oerlikon,  60  Ibs.  This  matter  of 
weight  is  oftentimes  an  important  one,  and  while  considering  the  weight 
of  transforming  apparatus  such  as  Mr.  Arnold  proposes,  and  such  as  I  pro- 
pose, I  wish  to  call  attention  to  the  fact  that  we  must  not  lose  sight  of 
the  consideration  that  for  the  same  maximum  operating  torque  with  satis- 
factory commutation  the  weight  of  motors  on  my  system  will  be  very 
materially  less  than  is  likely  to  be  realized  even  after  the  highest  per- 
fection of  the  single-phase  type,  and  that,  therefore,  there  is  quite  a  little 
margin  of  weight  at  that  point  available  to  compensate  for  the  weight  of 
the  motor  generator.  Furthermore,  I  consider  that  if  my  system  has  any 
virtue,  it  lies  principally  in  the  direction  of  the  production  of  a  very 
large  amount  of  power  upon  a  locomotive  and  the  possibility  of  con- 
trolling by  very  simple  means  a  multiple  of  very  heavy  locomotives,  where 
questions  of  simple,  uniform  acceleration  with  a  minimum  of  energy,  sim- 
plicity and  reliability  of  control  and  the  restoration  of  energy  are  con- 
siderations that  will  be  very  important. 

When  considering  heavy  locomotives  I  think  there  will  be  a  very  great 
advantage  to  be  found  in  a  system  such  as  mine,  which  employs  motors 
in  which  the  field  of  the  motor  is  entirely  independent  of  the  armature 
current.  What  I  mean  by  that  is  this, —  a  heavy  locomotive  will  be  worked, 
and  must  be  worked,  to  the  limit  of  its  maximum  tractive  effort,  and 
every  artifice  must  be  employed  to  secure  the  maximum  tractive  effort 
from  the  locomotive, —  the  same  is  true,  of  course,  of  the  steam  locomotive, 
— -and  the  result  is  the  parallel  rods  of  the  steam  locomotive,  which  are 
probably  the  chief  curse  of  the  steam  locomotive  to-day.  They  are  a  neces- 
sity in  order  to  secure  the  maximum  tractive  effort  with  a  certain  weight 
on  drivers.  With  series  motors  we  will  also  need  parallel  rods.  If 
we  attempt  to  leave  the  parallel  rods  off  it  will  be  evident  that  with 
perhaps  six  or  eight  drivers  on  a  side,  representing  six  or  eight 
different  motors,  some  one  of  those,  if  we  push  the  motors  to  the 
limit,  will  skid  before  the  rest,  and  when  it  does  so  skid  we  have 
a  condition  which  is  comparable  to  the  skidding  of  a  steam  locomotive 
by  too  rapid  opening  of  the  throttle,  and  it  becomes  necessary  to  stop, 
go  back  to  the  starting  condition  and  try  it  again.  Now,  that  is  due  to  the 
fact  that  a  series  motor  has  a  speed  which  is  dependent  upon  its  torque, 
a  speed  which  is  dependent  upon  the  current,  but  if  you  have  a  motor  with 
a  separately  excited  field  and  in  which  the  counter  volts  balance  the  im- 
pressed volts  without  any  rheostat  in  that  circuit,  it  is,  as  you  will  see, 
impossible  for  any  racing  away  of  the  motor  in  case  any  particular  motor 
does  tend  to  skid;  which  means  that  with  such  a  system  as  I  suggest 
we  can  operate  in  multiple  a  number  of  different  motors  and  secure  the 
effects  of  an  invisible  parallel  rod,  without  the  mechanical  complications 
and  handicaps  which  that  imposes  on  account  of  the  rigid  wheel-base 
and  the  consequent  difficulties  upon  the  curves.  Therefore,  I  think  that  the 
question  of  heavy  locomotive  practice  will  lead  strongly  in  the  direction  of 
a  separately  excited  field  or  some  other  artifice,  which  may  of  course  conic. 

ELEC.  RYS. 12. 


178  NIETHAMMER:     ELECTRIC    TRACTION. 

which  will  enable  us  to  secure  the  effects  of  the  parallel  rod  electrically, 
without  the  mechanical  difficulties. 

Mr.  W.  L.  WATERS  :  Referring  to  Mr.  Bragstad's  paper,  or  rather  to  the 
remark  in  that  paper  to  which  Mr.  Steinmetz  called  attention  —  that 
analytical  methods  are  necessary  for  dealing  with  problems  such  as  we 
have  in  the  single-phase  motor,  and  that  graphical  methods  are  of  little  use, 
it  has  always  seemed  to  me  that  it  is  more  a  question  of  a  natural  trend 
of  a  man's  mind  than  that  any  arbitrary  dogmatic  statement  can  be  made, 
either  that  the  analytical  or  that  the  graphical  method  is  the  only  one  to 
use.  Speaking  from  a  personal  point  of  view,  I  have  always  had  to  adopt 
analytical  methods  to  obtain  a  complete  and  comprehensive  understanding 
of  the  problem  in  the  first  place,  but  as  soon  as  it  comes  to  practical  de- 
signing, I  find  it  necessary  to  adopt  graphical  methods  and  rough  approxi- 
mate rules  obtained  from  experiments.  I  think  that  one  thing  students 
have  always  to  learn  before  they  can  become  practical  engineers  is  that 
designing  is  not  a  question  of  solving  differential  equations  dealing  in  com- 
plex functions  and  imaginaries,  but  one  of  deducing  rough  rules  from  ex- 
periment, and  from  previous  experience  with  similar  types  of  machines. 
As  it  has  been  very  aptly  put  —  designing  is  an  art,  rather  than  an  exact 
science. 

Coming  to  Mr.  Lincoln's  paper,  I  think  that  Mr.  Lincoln  hits  the  nail 
on  the  head,  when  he  states  that  directly  you  talk  about  potential  to 
earth,  instead  of  potential  between  conductors,  the  single-phase  system  is 
on  a  par  with  the  three-phase.  We  have  got  so  used  to  talking  about  three- 
phase  transmission  that  we  have  almost  come  to  believe  that  no  other 
system  of  transmission  is  possible.  The  original  three-phase  transmission 
work,  and  most  of  the  three-phase  distribution  work  at  the  present  time, 
has  been  done  with  three-phase  cables,  in  which,  of  course,  the  potential 
between  conductors  decides  the  strain  on  the  insulation.  But,  as  Mr. 
Lincoln  points  out,  when  we  come  to  modern  overhead  transmission  lines, 
it  is  the  potential  to  earth  that  decides  the  strain  on  the  insulation,  and 
this  being  the  case  the  single-phase  system  is,  for  overhead  work,  equal 
to  the  three-phase.  It  seems  peculiar  that  after  ten  years  or  so  of  almost 
exclusive  use  of  three-phase  system,  that  we  now  seem  likely  to  return  to 
the  original  single-phase  system,  which  has  been  continually  advocated  by 
Ferranti  and  which  was  used  in  the  first  commercial  transmission  —  the 
10,000-volt  Deptford-London  line. 

The  main  disadvantages  of  the  single-phase  system  are,  of  course,  obvious. 
That  with  a  single-phase  alternator  you  do  not  get  the  full  output  that 
the  machine  is  capable  of  giving,  and  that  the  single-phase  commutator 
motor  is  a  much  more  complicated  machine  and  much  more  liable  to  break 
down  than  the  three-phase  induction  motor.  These  disadvantages,  however, 
are  not  sufficiently  serious  to  prevent  the  single-phase  system  from  having 
a  wide  application. 

Dr.  STEINMETZ:  When  considering  the  development  of  a  new  field  in 
engineering,  we  first  consider  what  appears  to  be  the  simplest  and  the  best 
arrangement,  and  endeavor  to  introduce  that.  However,  in  every  case  we 
also  must  consider  the  existing  state  of  the  art,  what  has  been  before  and 
what  is  there.  If  a  cataclysm  to-morrow  should  wipe  out  all  our  civiliza- 


NIETHAMMER:     ELECTRIC    TRACTION.  17H 

tion  except  the  human  intelligence  and  we  should  then  proceed  unfettered 
by  existing  things  to  reconstruct  it,  we  would  do  very  many  things  differ- 
ently than  we  are  obliged  to  do  now.  One  of  these  features  my  friend  Mr. 
Armstrong  has  referred  to.  While  single-phase  generation  and  transmis- 
sion would  be  the  simplest,  the  enormous  magnitude  of  existing  three-phase 
plants  may  lead  us  to  utilize,  in  generation  at  least,  polyphase  systems.  It 
may  or  it  may  not.  The  future  alone  can  show  that.  There  are  a  number 
of  features  with  regard  to  the  use  of  commutator  motors  in  railway  work 
which  are  of  similar  character.  At  least  in  this  country  there  are  very  few 
villages  even  which  do  not  have  a  direct-current  railway  system.  After  all, 
the  electrification  of  the  steam  railway  has  not  made  such  progress  as 
enthusiasts  believed  it  would  ten  years  ago.  Electric  locomotives  have 
been  introduced  and  are  being  introduced,  but  in  most  cases  you  find 
special  requirements,  either  an  underground  tunnel  or  something  of  similar 
character.  But  what  has  taken  place  is  the  exact  counterpart  of  what 
took  place  three-quarters  of  a  century  ago.  The  early  attempts  of  the 
steam  locomotive  to  replace  the  horse  in  front  of  the  stage  coach  were 
not  successful,  but  a  new  motive  power  required  new  arrangements,  and 
the  steam  locomotive  and  the  railroad  train  has  been  developed.  The  horse 
has  not  disappeared  but  has  been  relegated  to  another  field.  You  see  the 
same  taking  place  now  in  electric  railroading.  You  do  not  see  in  general, 
at  least  not  yet,  the  electric  motor  replacing  the  steam  locomotive,  but 
you  see  the  trolley  car  paralleling  the  steam  railroad  and  either  taking 
away  a  certain  class  of  traffic  for  which  it  is  much  more  suited,  or  develop- 
ing a  traffic  of  its  own.  The  feature  whereby  the  trolley  car,  in  spite  of 
its  usually  lower  average  schedule  speed,  beats  the  steam  railway  train, 
is  the  absence  of  terminal  stations  and  the  absence  of  a  time-table.  With 
the  steam  railroad  train  you  have  to  go  to  the  depot,  and  you  have  to  con- 
sult beforehand  a  time-table. 

With  the  interurban  electric  railway  you  pick  up  the  car  anywhere 
in  the  city,  either  the  interurban  car  directly  or  a  transfer  car,  and  you 
do  not  look  for  a  time-table  but  wait  for  the  next  car  which  comes  along 
in  a  few  minutes.  That  is,  I  believe,  the  main  advantage  of  electric  rail- 
roading. But  as  soon  as  you  introduce  a  motor  which  is  specific  for  inter- 
urban service,  for  long-distance  travel,  which  cannot  run  over  your  city 
systems,  you  give  up  that  advantage  and  you  are  only  on  a  par  with  the 
steam  railroad  train.  Even  then  we  still  have  great  advantages  in  the 
rapidity  of  acceleration,  the  greater  schedule  speed  we  could  secure  with 
the  same  maximum  speed,  absence  of  smoke,  etc.  But  all  those  appear  to 
me  minor  advantages  compared  with  the  advantage  of  not  requiring  terminal 
station  and  time-table.  With  the  alternating  motor,  this  means  adapting 
the  new  systems  to  what  exists  at  the  present  day.  You  have  to  limit  the 
choice  of  your  motor  to  such  types  as  can  be  easily  applied  to  both  char- 
acters of  service.  Hence,  to  retain  the  main  advantages  of  electric  rail- 
roading, you  require  a  motor  that  will  run  equally  well  on  the  alternating, 
long-distance  trolley  circuit,  as  on  the  direct-current  city  distribution. 
That  is  one  of  the  features  on  which  you  have  to  compromise.  It  means 
that  you  must  carry  the  same  car,  the  same  motor,  with  equal  efficieney 
of  operation,  of  acceleration,  over  the  500-volt  city  system  and  over  the 


180  NIKTHA.MMKR:     ELECTRIC    TRACTION. 

high-voltage  long-distance  line.  This  feature,  and  this  class  of  service, 
determines,  to  a  certain  extent,  the  type  of  motor  and  gives  the  preference 
to  the  compensated  motor  or  Eickemeyer  motor  over  the  repulsion  motor, 
although  in  its  speed-torque  characteristics  some  advantages  exist  in  the 
latter.  For  other  classes  of  service,  as,  for  instance,  heavy  freight  service 
on  trunk  lines,  possibly  other  types  of  motors  may  be  preferable.  We  must 
consider  that  at  present,  after  the  development  of  nearly  a  quarter  of  a 
century,  one  type  of  motor  has  been  brought  forward'  and  everything  else 
dropped  to  practical  oblivion,  and  that  is  the  direct-current  series  motor, 
as  most  perfectly  fulfilling  all  the  requirements  of  electric  railroading 
as  it  is  at  present.  This  does  not  mean,  however,  that  it  will  remain  so. 
For  many  years  all  the  requirements  of  alternating  motors  have  been  ful- 
filled by  the  polyphase  induction  motor,  and  still  we  now  demand  a  single- 
phase  commutator  motor.  You  see,  there  may  be  fields  which  are  not 
touched  at  present,  but  which  will  have  to  be  taken  up  by  the  electrical 
engineer  in  railroading,  and  for  which  a  different  type  of  motor  may  be 
preferable.  All  the  classes  of  electric  railway  service  at  present,  whether 
it  is  the  city  tram  car  or  the  rapid  transit  road,  elevated  or  subway,  or 
the  suburban  or  interurban  service,  are  very  similar  in  their  characteristics. 
They  all  require  a  motor  which  is  able  to  give  a  very  high  torque,  that 
is,  a  very  rapid  acceleration,  sustained  up  to  a  considerable  speed,  and 
beyond  this  speed,  at  the  end  of  the  high  acceleration,  a  torque  curve  which 
decreases  very  rapidly  but  still  extends  to  considerably  higher  speeds, 
running  down  to  20  per  cent  or  less  of  the  torque  of  acceleration  at  twice 
the  speed  which  is  reached  by  full  acceleration  torque.  In  addition  thereto 
you  require  means  to  operate  efficiently  at  moderate  torque  and  low  speeds, 
which  is  fulfilled  by  the  series-parallel  connection.  In  city  tram  car  work 
you  have  to  stop  very  frequently,  at  very  irregular  intervals.  Therefore 
you  have  to  be  able  to  accelerate  very  rapidly,  with  heavy  acceleration, 
so  as  to  maintain  good  schedule  speed.  You  must  have  rapid  accelera- 
tion up  to  considerable  speed  and  then  get  the  benefit  of  favorable  con- 
ditions of  road  by  running  up  to  high  speed  with  decreasing  torque.  The 
torque  must  decrease  rapidly  at  high  speeds,  because  otherwise  on  a  level 
stretch  you  would  either  have  to  cut  in  and  cut  out  continuously  or  you 
would  run  to  such  speeds  as  were  beyond  your  motor  capacity.  Further- 
more, in  districts  of  heavy  traffic  you  have  to  run  slowly.  This  means 
series-parallel  control.  When  you  come  to  suburban  or  interurban  service, 
you  have  the  same  characteristic  except  that  the  speeds  are  higher,  and 
the  stops  less  frequent.  In  rapid  transit,  you  have  again  the  same  char- 
acteristic, only  larger  motors  and  higher  speeds.  Now,  the  induction  motor 
gives  you  also  a  sustained  acceleration  but  a  torque  which  drops  down  to 
zero  immediately  above  the  speed  reached  with  full  acceleration  torque. 
That  is  that  part  of  the  speed  curve  from  the  end  of  maximum  acceleration 
to  the  speed  of  free  running  (about  twice  the  former  speed),  or  the  accelera- 
tion on  the  motor  curve,  does  not  exist  with  the  induction  motor.  Accelera- 
tion on  the  motor  curve,  however,  is  the  most  efficient  acceleration.  You 
cannot  go  beyond  synchronous  speed  and  so  cannot  get  the  benefit  of  the 
track,  with  the  induction  motor.  Now,  you  can  indeed  extend  your  curve 
by  making  synchronism  the  free  running  speed.  But  that  means  that  you 


2V 1 ET 'HAMMER:     ELECTRIC    TRACTION.  181 

have  half  the  rate  of  acceleration,  assuming  the  same  size  of  motor,  or 
if  you  desire  the  same  high  acceleration,  you  require  twice  as  large  a 
motor,  which  obviously  is  not  feasible,  because  usually  you  have  not  the 
space.  Hence,  where  you  have  to  accelerate  rapidly  to  high  speeds,  where 
you  have  to  get  the  benefit  of  favorable  conditions  of  the  road,  the  poly- 
phase induction  motor  is  not  successful.  Under  favorable  conditions,  for 
instance  for  the  class  of  work  where  the  acceleration  curve  does  not  differ 
much  from  the  running  curve,  as  on  heavy  grades,  on  mountain  railways, 
as  mining  locomotives,  where  indeed  the  character  of  the  work  is  not  rail- 
way work  but  rather  elevator  work,  there  the  three-phase  motor  is  success- 
ful, and  there  are  mountain  railways  in  existence  in  this  country,  as  well 
as  abroad, —  with  three-phase  induction  motors.  But  that  is  not  regular 
railway  service.  The  different  alternating-current  commutator  motors  give 
a  torque  curve  very  similar  to  that  of  the  direct-current  series  motor,  ex- 
cept that  the  torque  decreases  slightly  less  with  the  increase  of  speed,  the 
torque  curve  as  function  of  the  speed  is  less  steep  (the  induction  motor  as 
stated  gives  practically  a  vertical  line ) .  The  repulsion  motor,  as  stated 
in  my  paper,  gives  the  steepest  curve;  the  plain  series  motor,  without  com- 
pensation, the  flattest  curve.  The  result  hereof  is  that  with  the  same 
speed  of  free  running,  the  alternating-current  commutator  motor,  with  the 
same  acceleration  torque,  will  not  sustain  the  acceleration  up  to  quite  the 
same  high  speed  as  the  direct-current  motor,  but  will  strike  the  motor 
curve  at  a  lower  speed.  This  gives  a  higher  efficiency  of  acceleration,  but 
with  the  same  maximum  acceleration,  the  average  acceleration  will  be  less, 
and  so,  to  get  up  to  the  same  speed,  it  will  take  a  slightly  longer  time  with 
the  alternating-commutator  motor  than  with  the  direct-current  series 
motor,  but  the  acceleration  will  be  more  efficient;  because  the  larger  part 
of  the  acceleration  is  on  the  motor  curve.  Where  you  are  able  to  increase 
the  maximum  acceleration  you  can  get  the  same  average  acceleration  with 
the  alternating-current  motor  as  with  the  direct-current  series  motor, 
and  that  at  higher  efficiency,  other  things  being  equal,  in  the  alternating 
motor,  but  you  have  to  go  to  higher  maximum  values  of  acceleration. 
Hence  where  you  are  limited  by  the  comfort  of  the  passengers  you  cannot 
do  that,  and,  therefore,  for  some  classes  of  service,  where  you  have  to  ac- 
celerate at  the  maximum  value  permitted  by  the  comfort  of  the  passenger, 
the  direct- current  series  motor  gives  you  a  more  rapid  average  acceleration 
than  the  ordinary  alternating  commutator  motor.  This,  however,  does  nob 
preclude  the  alternating-current  commutator  motor  being  modified  so  as  to 
give  the  same  characteristic  as  the  direct-current  series  motor  and  that  is 
being  done.  But  the  motor  as  it  is  in  service  at  present  gives  a  torque 
curve  of  slightly  less  steepness  than  the  average  direct-current  series  motor. 
The  counterpart  of  this  lesser  steepness  of  the  torque  curve  of  the  alter- 
nating-commutator motor  is  that  you  can  run  over  a  wider  range  of  speed 
with  the  same  resistance,  or  the  same  potential. 

Mr.  LAMME:  Several  points  have  been  brought  up  since  I  spoke  last, 
in  connection  with  the  fact  that  we  have  had  to  adapt  this  single-phase 
railway  system  to  existing  conditions.  It  has  been  mentioned  that  single- 
phase  would  be  preferable  to  polyphase,  both  for  generation  and  transmis- 
sion, but  that  the  system  has  to  be  adapted  to  existing  generating  plants 


182  NIETHAMMER:     ELECTRIC    TRACTION. 

and  that  the  nearest  approach  we  could  make  to  the  ideal  system  would  be 
to  transmit  at  three-phase  from  existing  stations,  transform  to  two- 
phase,  and  feed  each  of  the  two  phases  to  the  trolley  as  independent  single- 
phase  lines.  In  connection  with  the  use  of  single-phase  throughout,  it  may 
be  of  interest  to  go  back  to  the  first  paper  on  single-phase  railway  motors 
of  the  commutator  type  which  was  presented  two  years  ago  this  month, 
before  the  American  Institute.  In  that  paper  I  called  attention  to  the 
fact  that  the  Westinghouse  Company  had  taken  a  contract  for  a  single- 
phase  railway  using  commutator  type  motors.  Among  the  various  features 
of  the  system  as  described,  it  should  be  noted  that  our  proposition  was  for 
single-phase  throughout,  the  generators  being  wound  for  single-phase  15,000 
volts,  and  feeding  directly  into  the  transmission  circuit.  Step-down  trans- 
formers were  to  be  used  in  the  sub-stations,  or  transforming  stations,  and 
single-phase  current  was  fed  to  the  trolley  circuit  and  to  the  motors. 
That  was  considered  an  ideal  system,  and  such  an  arrangement  could 
be  adopted  in  this  particular  case  because  the  road  was  a  new  one  through- 
out, and  was  not  limited  to  any  extent  by  existing  conditions.  But  most 
of  the  projects  which  have  been  brought  up  since  that  time  have  been 
in  connection  with  existing  power-plants,  or  are  roads  which  expect  at 
sffrne  future  time  to  tie  up  with  other  plants,  so  we  have  been  obliged  to 
accept  the  polyphase  generating  and  transmission  plants  with  the  single- 
phase  distribution  beyond  the  power-house,  or  the  transforming  stations. 
Take  for  example  a  single-phase  road  which  is  now  being  installed  between 
Cincinnati  and  Indianapolis.  The  company  installing  this  had  already 
bought  machinery  for  a  three-phase  generating  plant  with  direct-current 
distribution  from  converters.  They  changed  over  to  the  single-phase  system 
after  the  machinery  was  partly  completed.  It  was  suggested  that  a  straight 
single-phase  plant  throughout  would  present  many  advantages,  but  the 
customer  could  not  see  his  way  clear  to  make  the  change  so  late  in  the 
day.  Therefore  the  customer  decided  to  stick  to  the  three-phase  generating 
and  transmitting  plant  with  transformation  to  two-phase  in  the  sub- 
stations. The  line  is  divided,  one  branch  being  fed  from  one  phase,  and 
the  other  branch  from  the  other  phase.  We  have  found  that  similar  con- 
ditions hold  true  in  many  other  plants.  Another  condition  which  came 
up  in  some  of  the  earlier  projects  was  that  the  customers  were  some- 
what doubtful  of  the  single-phase  system  on  account  of  its  novelty,  and  they 
took  the  stand  that  if  they  put  in  three-phase  generation  and  transmission, 
they  would  always  be  in  position  to  adopt  rotary  converters  afterward,  if 
they  found  it  desirable  to  do  so.  We  have  heard  but  little  on  this  point  in 
the  past  year  or  two. 

Mr.  E.  KILBUBN  SCOTT:  How  do  you  change  the  three-phase  into  single- 
phase  on  the  line  you  speak  of? 

Mr.  LAMME:  Consider  one  branch  of  the  line  in  one  direction  from  the 
power-house  as  one  phase,  and  the  other  branch  in  the  opposite  direction 
as  the  other  phase. 

Mr.  SCOTT:  Can  you  transform  from  three-phase  to  single-phase  with 
transformers?  Can  it  be  done  like  the  three-phase  two-phase  arrangement? 

Mr.  LAMME:      Well,  that  I  am  not  prepared  to  say.     Another  feature 


NIETHAMMER:     ELECTRIC    TRACTION.  183 

worth  considering  in  the  Baltimore-Annapolis  road  was  the  frequency 
adopted.  At  that  time  we  proposed  a  frequency  of  about  two-thirds  of 
what  is  used  at  present.  That  frequency  was  then  considered  as  the 
most  suitable  one  taking  everything  into  consideration,  as  it  was  better 
for  the  motors,  transmission  line,  and  for  the  generators.  I  still  hold  to 
the  opinion  that  for  the  motors  a  low  frequency  is  better  than  a  higher 
frequency,  especially  for  larger  capacities  of  motors,  and  I  think  that  as 
we  take  up  heavy  locomotive  work  that  this  question  of  a  frequency  lower 
than  twenty-five  cycles  will  be  found  of  great  importance.  It  is  entirely 
possible  than  when  the  steam  roads  are  electrified  it  will  be  found  advisable 
to  adopt  some  frequency  other  than  twenty-five  cycles.  In  a  great  many 
cases  the  power-plant  requirements  for  the  heavy  railroads  will  be  so  great 
compared  with  existing  plants  that  these  systems  can  adopt  their  own 
frequency.  It  was  found  that  in  pushing  the  lower  frequency,  it  was  much 
the  same  as  in  pushing  the  single-phase.  We  could  not  get  people  to  adopt 
it,  largely  on  account  of  utilization  of  existing  plants.  We  found  that  was 
the  greatest  objection  to  low  frequency.  We  found  that  even  in  the  case  of 
heavy  railroads,  with  plants  of  four  or  five  times  the  capacity  of  all  the 
other  plants  in  the  same  district,  they  nevertheless  wished  to  start  out 
with  a  frequency  which  corresponds  with  that  of  the  smaller  plants  in  the 
same  neighborhood.  I  think  they  will  pull  away  from  that  policy  some 
day. 

Another  point  brought  out  in  the  Institute  paper  referred  to  was  that 
the  type  of  alternating-current  motor  to  be  used  was  perfectly  adapted  for 
operation  on  direct-current,  as  it  was  primarily  a  high  class  direct-current 
machine.  It  was  stated  that  the  complication  necessary  for  operating  on 
both  alternating  and  direct  currents  was  much  greater  than  for  either 
the  alternating  or  direct  current  alone;  because  it  was  necessary  to  have 
rather  complicated  switching  devices  for  throwing  from  one  system  to  the 
other,  if  the  combination  system  was  used.  At  that  time  it  was  thought 
that  such  an  arrangement  would  be  entirely  too  complicated,  and  that 
railway  engineers  could  not  possibly  accept  it;  yet  within  a  comparatively 
short  time  after  the  publication  of  that  paper,  we  found  engineers  who  were 
willing  to  consider  it,  and  within  the  past  year  contracts  have  been  closed 
with  roads  which  are  to  be  operated  on  alternating  current  on  suburban 
and  interurban  service  and  direct  current  on  the  city  service,  and  the  extra 
complication  of  such  a  system  does  not  seem  to  be  prohibitive  to  them. 
The  series-parallel  connection  of  motors  was  considered  for  this  service. 
We  found  that  on  many  of  the  projects  there  was  no  particular  advantage 
with  such  an  arrangement.  In  one  large  road  which  we  are  installing,  the 
service  across  country  will  be  at  a  very  high  speed,  and  it  was  found  that 
to  get  the  necessary  low  speed  in  the  direct-current  city  lines  it  was  neces- 
sary to  connect  all  four  motors  in  series.  Therefore,  there  was  no  advantage 
in  operating  series-parallel  on  the  direct-current  part  of  the  road  as  only 
the  series  combination  could  be  used.  We,  therefore,  adopted  the  combina- 
tion with  four  motors  in  series  for  the  direct-current  and  four  motors  in 
parallel  for  the  alternating  service,  and  speed  variation  on  the  alternating 
service  is  obtained  by  means  of  a  number  of  loops  or  taps  on  the  lowering 
transformers.  In  this  way  we  obtain  on  the  alternating-current  service 


184  NIETHAMMER:     ELECTRIC    TRACTION. 

better  conditions  than  could  be  obtained  with  series-parallel,  as  we  have 
more  than  two  efficient  running  steps  and  the  starting  conditions  are  also 
better.  I  think  that  where  the  speed  on  suburban  service  is  comparatively 
low,  it  might  be  possible  to  use  the  series-parallel  arrangement  of  motors, 
with  the  motors  thrown  in  series  on  the  city  service  on  direct  current,  but 
we  have  found  in  general  that  in  going  into  the  cities,  or  through  towns 
which  are  not  of  large  size,  in  many  cases  a  similar  arrangement  has 
been  to  put  up  an  extra  trolley  wire  alongside  the  direct- current  trolley 
wire,  this  extra  wire  being  supplied  with  alternating  current  at  about  500 
volts.  By  placing  one  of  the  transforming  stations  near  the  junction 
of  the  suburban  and  the  city  service,  we  can  feed  the  500-volt  city  trolley 
wire  from  a  low  voltage  tap  on  the  lowering  transformer.  In  this  way 
we  can  have  low-voltage  and  high-voltage  trolleys  supplied  from  the  same 
transforming  station.  On  the  lowering  transformer  on  the  car  itself, 
we  have  also  a  low-voltage  tap  corresponding  to  the  voltage  on  the  city 
trolley.  When  the  car  is  to  be  changed  from  the  high-voltage  trolley  to  the 
low-voltage,  the  circuit  is  switched  over  to  the  low  tap  on  the  car  trans- 
former and  the  same  control  apparatus  is  used  as  for  the  suburban  high- 
voltage  service.  That  has  proved  to  be  a  very  simple  arrangement,  and  it 
has  been  adopted  on  most  of  the  roads  which  we  have  sold.  About  seven 
or  eight  roads  have  been  sold  which  utilize  such  an  arrangement,  and  very 
few  have  so  far  found  necessity  for  the  extra  complication  which  will  be 
required  for  operation  of  both  alternating  and  direct  currents. 

In  the  preceding  discussions,  there  seems  to  have  been  no  particular 
comment  on  the  question  of  the  most  suitable  frequency.  Twenty-five 
cycles  seems  to  be  the  most  suitable  frequency  at  the  present  time  for 
commercial  work,  simply  because  existing  plants  have  been  installed  with 
this  frequency.  It  is  possible  to  go  to  somewhat  higher  frequencies  suc- 
cessfully with  a  somewhat  larger  motor,  but  with  corresponding  poorer 
performance.  Better  results  can  be  obtained  from  the  motor  at  lower 
than  twenty-five  cycles,  but  such  lower  frequency  will  possibly  not  be 
adopted  extensively  until  we  get  into  heavy  railroad  work.  But  if  we 
should  adopt  lower  frequency,  and  thus  break  loose  from  existing  systems, 
then  will  be  the  time  when  we  can  also  adopt  the  straight  single-phase 
system. 

Mr.  A.  H.  ARMSTRONG:  Mr.  Chairman,  the  product  of  the  engineer  is  at 
the  best  a  compromise.  With  the  rest  of  us,  Mr.  Lamme  has  gone 
through  the  battle  of  frequencies,  starting  at  125  and  130  cycles  per 
second  with  a  gradual  reduction  to  25  cycles,  until  we  thought  the 
bottom  had  been  struck,  but  there  are  certain  advantages  which  perhaps 
warrant  the  introduction  of  16  2/3  cycles,  or  even  lower.  I  believe  15 
cycles  is  already  in  operation  on  the  other  side  of  the  water. 

Closely  allied  to  the  confusion  of  frequencies,  is  the  babel  of  voltages. 
Contrasted  with  the  two  accepted  standard  frequencies  of  twenty-five  and 
sixty  cycles,  there  are  the  multitude  of  standard  voltages  with  their  modifi- 
cations. Voltages  are  at  the  best  mixed  up,  and  no  new  distributing  system 
can  go  in  unless  it  takes  account  of  the  voltages  existing  in  neighboring 
plants  with  which  it  may  be  consolidated  at  some  future  theoretical  date, 
a  possibility  always  kept  fully  in  mind  by  the  promoters  of  the  new 


NIETHAMMER:     ELECTRIC    TRACTION.  185 

installation.  But  in  adopting  alternating- current  motors  for  railway 
work,  we  have  an  open  field  so  far  as  trolley  voltages  are  concerned,  and 
I  am  glad  to  see  that  there  is  a  fairly  uniform  movement  toward  adopt- 
ing 2200  and  3300  volts  as  the  two  standards.  I  do  not  quite  see  how 
we  can  adopt  one  of  these  in  preference  to  the  other,  but  it  seems  neces- 
sary perhaps  to  adopt  both  of  them  for  the  present,  and  by  a  gradual 
course  of  elimination  to  settle  on  one  as  being  the  best  fitted  for  general 
work. 

As  regards  the  fitness  of  the  alternating-current  motor  for  railway 
work  or  its  proper  field  of  action,  very  little  has  been  said  this  morning 
beyond  Mr.  Steinmetz'  remarks,  and  I  would  like  to  supplement  them 
by  two  or  three  observations  of  my  own.  I  have  been  fortunate  in  having 
an  insight  into  the  probable  plans  of  a  steam-operated  road  which  is 
going  to  change  over  part  of  its  service  to  electrical  operation.  The 
engineers  in  charge  of  the  work  are  very  progressive,  and  seem  to  con- 
sider nothing  but  the  alternating-current  motor  as  available. 

Another  thing  that  strikes  me  as  instructive  is  the  fact  that  although 
they  have  their  own  private  right  of  way,  their  own  terminal  stations 
and  are  entirely  isolated  from  any  influences  of  direct-current  city  work, 
they  will  consider  nothing  but  the  operation  of  alternating-current  motors 
on  direct-current  circuits.  The  road  is  being  electrically  equipped  to 
take  care  of  the  suburban  passenger  traffic,  the  changing  over  of  locomo- 
tives for  handling  freight  traffic  not  yet  being  contemplated.  They  realize 
fully  that  their  receipts  have  been  eaten  into  very  heavily  by  the  inroads 
of  parallel  electric  lines,  all  of  which  have  the  right  of  way  over  city 
streets.  The  success  of  these  roads  is  due  largely  to  the  fact  that  they 
can  pick  up  and  discharge  passengers  on  city  streets,  and  the  steam  road 
management  do  not  consider  it  feasible  to  give  up  one  of  the  most  valu- 
able assets  now  enjoyed  by  the  electric  roads.  In  operating  their  system 
electrically,  therefore,  they  are  considering  the  giving  up  either  in  whole 
or  part  of  their  terminal  stations  and  the  operation  of  their  cars  on  their 
own  private  right  of  way  between  cities  and  over  the  city  streets  at  the  ter- 
minals, in  fact  duplicating  almost  exactly  the  present  operation  of  our 
city  and  suburban  systems. 

Mr.  Lamme  made  a  remark  about  the  advisability  of  installing  a  sepa- 
rate alternating-current  trolley  system  in  small  towns  en  route,  although 
they  may  have  a  present  tramway  system  operated  by  direct  current.  It 
seems  to  me  that  the  trend  of  progress  in  alternating-current  motor  work 
necessitates  that  these  motors  must  operate  over  city  systems  with  direct 
current.  I  have  a  case  in  mind  where  a  road  was  to  be  operated  on  the 
suburban  sections,  some  thirty  or  forty  miles,  with  alternating  current, 
connecting  two  city  systems  at  the  termini.  The  expense  and  complication 
of  introducing  a  separate  alternating-current  trolley  in  the  cities  was  very 
great,  the  expense  not  being  so  much  of  a  consideration  as  the  com- 
plications of  equipping  every  street  in  the  city  leading  to  the  car  barns, 
and  in  fact  any  route  liable  to  be  taken  by  the  suburban  cars. 

In  adopting  an  alternating-current  motor  system  that  is  applicable  to 
general  work,  the  first  consideration  is  of  course  to  have  it  operative;  the 
second  is  to  simplify  the  character  of  the  mechanism  and  controlling  ap- 


18G  NIETHAMMER:     ELECTRIC    TRACTION. 

paratus  as  much  as  possible.  If  a  motor  control  is  adopted  that  will  be 
operative  on  both  alternating-current  and  direct-current  circuits,  it  may 
or  may  not  necessitate  giving  up  the  advantages  of  potential  control.  Sim- 
plification \vould  call  for  plain  rheostatic  control  similar  to  that  em- 
ployed now  in  the  operation  of  direct-current  motors.  In  fact,  motors 
are  in  commercial  operation  using  plain  rheostatic  series-parallel  con- 
trol both  for  alternating-current  and  direct-current  circuits,  the  control 
being  identical  in  each  case,  and  effected  by  a  standard  direct-current  con- 
troller with  slight  adaptation,  the  only  change  made  being  the  cutting 
out  of  the  blow-out  magnet  when  alternating  currents  are  used. 

Mr.  Steinmetz  pointed  out  the  advantage  enjoyed  by  alternating-current 
motors  of  a  more  flexible  speed-torque  curve  than  that  met  with  in  the 
design  of  direct-current  motors.  This  makes  it  possible  to  accelerate  to 
the  full  rheostatic  point  with  fewer  steps,  in  less  time  and  with  less  re- 
sistance loss  than  is  possible  with  direct-current  control.  It  furthermore 
simplifies  greatly  the  control  of  motors  when  operating  a  combined  alter- 
nating-current-direct-current system.  Ordinarily,  series-parallel  control  is 
not  placed  at  such  a  disadvantage  in  regard  to  efficiency  of  acceleration 
compared  with  potential  control  of  alternating  currents.  This  is  espe- 
cially true  considering  the  extra  apparatus  required,  if  induction-regulator 
control  is  used,  or  the  extra  complication  involved  if  potential  control  is 
effected  by  taps  off  the  main  step-down  transformer. 

There  are  two  general  fields  for  alternating-current  motors  presenting 
themselves  for  immediate  notice;  the  suburban  field,  calling  for  a  motor 
capable  of  operating  with  direct  current  over  city  streets,  because  such 
roads  depend  upon  city  traffic  and  frequent  stops  for  their  success;  and 
the  second  field  is  either  main-line  freight  work,  or  the  more  immediate 
problem  of  our  mountain  grades.  In  the  latter  case  the  road  is  entirely 
isolated  from  any  direct-current  influences;  it  does  not  cater  to  local  pas- 
senger traffic,  but  is  used  for  through  haulage  only;  there  are  no  senti- 
mental resources  influencing  the  adoption  of  electricity,  but  it  is  installed 
purely  from  financial  considerations  of  lower  operating  cost  compared  with 
steam  locomotives.  On  this  class  of  road  it  seems  probable  that  the 
operation  of  motors  on  direct-current  circuits  will  not  have  any  influence 
in  determining  the  motor  to  be  used.  The  system  is  purely  alternating 
throughout,  operates  at  practically  a  constant  output,  no  accelerating 
problems  are  present,  and  potential  control  is  very  convenient  and  effective 
for  controlling  motors. 

Mr.  Leonard  brought  up  the  point  of  the  weight  of  the  alternating- 
current  equipment  compared  with  direct  current.  At  present,  such  equip- 
ments weigh  approximately  25  to  30  per  cent  more  than  direct-current 
equipments  of  equal  capacity.  This  increased  weight,  while  it  has  an 
effect  upon  the  first  cost  of  the  apparatus,  has  very  little  effect  upon 
the  operation  of  such  roads  as  are  influenced  by  the  adoption  of  alter- 
nating-current motors.  The  alternating-current  motor  is  essentially  a 
suburban  or  high-speed  motor,  or  else  a  freight  motor.  It  is  not  in- 
tended for  city  work,  not  being  so  well  adapted  for  this  class  of  service  as 
the  direct-current  motor  with  its  lower  internal  losses  in  acceleration. 


NIETHAMMER:     ELECTRIC    TRACTION.  187 

A  car  weighing  thirty  tons,  say,  with  direct-current  apparatus,  and  thirty- 
three  or  thirty-four  tons  with  alternating  apparatus,  will  require  practi- 
cally the  same  energy  when  operating  at  a  maximum  speed  of  forty-five 
or  fifty  miles  an  hour.  In  other  words,  a  slight  increase  in  the  weight  of 
the  car  will  not  greatly  influence  the  watt-hours  per  ton  mile  required 
by  that  car  when  effecting  a  given  schedule  on  our  suburban  systems. 
In  city  work,  however,  an  increase  of  10  per  cent  in  the  weight  of  the  car 
calls  for  fully  10  per  cent  increase  in  the  energy  consumption,  due  largely 
to  the  fact  that  the  wind  friction,  which  is  the  controlling  factor  in  high- 
speed service,  is  almost  entirely  eliminated  at  the  low  speed  incident  to 
city  traffic,  and  the  energy  consumed  by  the  car  goes  up  in  direct  proportion 
to  its  weight.  The  weight  of  the  alternating-current  apparatus,  therefore, 
cannot  be  brought  up  as  an  argument  against  its  adoption  in  the  practical 
work  for  which  the  alternating-current  motor  is  primarily  adapted. 

Mr.  H.  WARD  LEONARD:  The  closing  remark  which  Mr.  Armstrong 
made  was  to  the  effect  that  for  rapid  acceleration  work  the  increased 
weight  of  the  alternating-current  motor  would  be  a  serious  handicap  to 
it,  that  the  increased  weight  of  the  car  would  require  increased  energy 
in  direct  proportion  to  that  increase  of  weight.  I  should  like  to  say  in 
reply  to  that,  that  that  remark  is  not  broadly  true,  as  it  would  not  be 
true  in  the  case  of  such  systems  as  restore  a  considerable  portion  of  the 
energy  required  for  the  acceleration,  during  the  period  of  retardation, 
which,  of  course,  is  one  of  the  points  I  urge  most  strongly  in  connection 
with  my  system. 

Mr.  P.  M.  LINCOLN:  The  company  which  I  represent  have  until  re- 
cently recommended  a  trolley  voltage  no  higher  than  1100,  for  the  reason 
that  we  believe  that  a  voltage  of  such  nature  will  not  require  a  complete 
modification  of  the  trolley  line  insulation.  The  same  style  of  trolley  in- 
sulation as  is  used  on  the  present  500  volts  will,  we  believe,  be  suitable 
when  properly  reinforced  for  a  voltage  of  1100  volts  alternating.  But  on 
going  to  the  higher  trolley  voltages  which  have  been  mentioned,  viz.,  2200 
and  3300,  we  are  of  the  opinion  that  the  ordinary  insulation  as  at  present 
used  on  500  volts  will  not  answer,  nor  will  the  type  of  insulation  answer. 
It  will  require  some  new  type  of  trolley  insulation.  For  that  reason  we 
have  recommended  that  the  trolley  voltage  be  not  increased  to  these 
higher  voltages  until  a  new  type  of  insulation  has  been  developed.  That 
was  at  the  beginning.  As  it  stands  now,  however,  the  new  types  of 
trolley  insulation  have  been  developed,  and  there  is  no  bar  to  the  increase 
in  trolley  voltage  to  2200  or  3300.  The  trolley  voltage  is  bound  to  in- 
crease. As  the  requirements  of  the  circuit  increase  the  best  and  the 
easiest  way  to  take  care  of  it  is  by  increasing  the  trolley  voltage.  It  is 
a  problem  which  is  bound  to  come. 

I  was  considerably  interested  in  Mr.  Armstrong's  remarks  concerning 
the  controller  for  a.  c.  cars  which  has  been  proposed,  viz.,  using  the 
ordinary  direct-current  controller  for  alternating  currents  by  simply 
cutting  out  the  blow-out  magnets.  It  seems  to  me  that  that  is  a  step 
to  the  rear.  A  good  many  years  ago  when  controllers  were  in  their  in- 
fancy, the  blow-out  magnet  was  not  used,  and  in  order  to  make  a  suc- 
cessful controller  the  blow-out  magnet  was  almost  an  absolute  necessity. 


188  NIETHAMMER:     ELECTRIC    TRACTION. 

It  has  been  my  experience,  as  well  as  the  experience  of  those  with  whom  I 
have  been  associated,  that  it  is  considerably  harder  to  take  care  of  con- 
tacts which  are  operating  with  alternating  current  than  of  those  which 
are  operating  with  direct  current.  The  alternating  current  will  bite  into 
the  contact  pieces,  other  conditions  being  equal,  considerably  more  than 
the  direct  current  will.  Therefore,  I  do  not  see  how  an  ordinary  controller 
which  requires  a  blow-out  magnet  for  direct  current  is  going  to  operate 
successfully  when  used  on  alternating  current  without  any  apparatus  to 
interrupt  or  to  cut  down  the  deleterious  effects  of  the  spark.  Possibly 
for  small  equipments  such  an  arrangement  will  operate  satisfactorily,  but 
when  the  amount  of  power  involved  is  large,  as  it  is  in  the  larger  sizes 
of  equipments,  I  do  not  see  how  such  a  scheme  of  control  will  operate 
satisfactorily. 


NOTES  ON  EQUIPMENT  OF  THE  WILKESBABEE 
&  HAZELTON  RAILWAY. 


BY  LEWIS  B.  STILLWELL. 


The  equipment  of  the  Wilkesbarre  &  Hazleton  Railway,  which 
was  completed  in  the  spring  of  1903,  has  been  referred  to  in  some 
detail  in  technical  publications,  but  it  is  thought  that  a  brief  ' 
description  of  certain  features,  novel  in  whole  or  in  part,  particu- 
larly the  covered  third  rail  and  the  special  form  of  collecting 
shoe  employed,  should  be  recorded  in  the  proceedings  of  this 
Congress.  The  fact  that  this  was  the  first  railway  of  any  consid- 
erable length  in  America  to  be  equipped  for  commercial  use  with 
a  protected  third  rail,  and  that  for  the  last  18  months  it  has 
been  in  highly  successful  operation  may  make  the  following  de- 
scriptive notes  relative  to  construction  and  to  performance  of  some 
value  to  engineers  who  may  be  called  upon  to  deal  with  similar 
equipment  problems. 

The  more  important  noteworthy  features  of  this  railway  and  its 
equipment  are: 

1).  The  use  of  a  contact  rail  covered  by  a  plank  guard  to  protect 
it  against  snow  and  sleet,  and  to  prevent  accidental  contact  by 
people  crossing  the  track  or  walking  near  it; 

2).  The  elimination  of  all  grade  crossings; 

3).  The  fact  that  it  traverses  a  rugged  and  mountainous  country, 
level  stretches  of  roadbed  being  practically  insignificant,  while 
there  are  several  stretches  of  3  per  cent  grade  not  less  than  four 
miles  in  length; 

4).  The  use  of  cars  weighing  42  tons,  net,  without  passenger 
load,  and  equipped  with  four  motors  of  125  horse-power  (one  hour 
rating)  each; 

5).  Brake  equipment  so  designed  that  no  one  accident  to  any 
part  of  the  rigging  can  render  all  brakes  inoperative; 

6).  The  use  of  a  portable  converter  station  in  the  form  of  a  car 
carrying  transformers,  converters  and  necessary  switch  gear; 

7).  The  use  of  a  soldered  —  not  riveted  —  rail  bond. 

[189] 


190      8TILLWELL:     WILKESBARRE  d  HAZELTON  RAILWAY. 


.  1. 


STILL  WELL:     WILKESBARRE  d  HAZELTON  RAILWAY.      191 

DESCRIPTION  or  RAILWAY  AND  EQUIPMENT. 

The  railway  is  26.2  miles  long,  has  a  single  track  and  connects 
the  cities  of  Wilkesbarre  and  Hazleton  in  northwestern  Pennsyl- 
vania. It  competes  with  two  steam  railways,  the  Lehigh  Valley 
and  a  branch  of  the  Pennsylvania,  both  of  which  were  in  operation 
long  before  their  electrically  equipped  competitor  was  projected. 
The  maximum  grades  used  by  the  steam  railways  approximate 
2  per  cent,  and  the  distance  between  their  respective  terminals  in 
the  two  cities  is  50.4  miles  in  the  case  of  the  Pennsylvania  and  49.6 
miles  in  the  case  of  the  Lehigh  Valley.  The  country  between 
Wilkesbarre  &  Hazleton  is  mountainous,  the  new  railway  being 
compelled  to  cross  not  less  than  three  ranges,  as  shown  in  profile, 
Fig.  2.  The  routes  of  the  three  competing  lines  are  shown  in  the 
map,  Fig.  1.  As  will  be  seen  by  reference  to  Fig.  2  the  terminus 


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FIG.  2.  —  PROFILE  OF  PRELIMINARY  LOCATION. 

of  the  line  in  Hazleton  is  nearly  1200  feet  above  the  Wilkesbarre 
terminus.  One  of  the  striking  advantages  of  electric  traction  is 
illustrated  by  the  fact  that  the  adoption  of  a  practically  uniform 
gradient  of  3  per  cent  has  made  it  possible  to  locate  and  construct 
a  line  but  26.2  miles  in  length,  connecting,  through  so  exceptionally 
mountainous  a  country,  termini  which  are  21  miles  apart  as  the 
crow  flies.  In  accomplishing  this  result,  one  tunnel  is  used;  this 
pierces  the  Penobscot  range,  as  shown  on  the  profile,  and  is  2684 
ft.  in  length. 

The  passenger  traffic  of  the  road  is  chiefly  through  service,  the 
country  between  the  two  cities  being  sparsely  populated.  A  con- 
siderable freight  business  in  delivery  of  supplies  to  the  inhabitants 


192       STILLWELL:      WILKESBARRE  d  HAZELTON  RAILWAY. 

of  the  intervening  country  and  in  hauling  farm  produce  to  market 
as  well  as  a  moderate  express  business  has  been  developed  since  the 
service  of  this  road  was  inaugurated. 

The  railway  is  constructed  upon  a  private  right  of  way  60  ft. 
wide,  fenced  on  both  sides  throughout  its  entire  length.  Grade 
crossings  are  entirely  eliminated,  a  feature  of  construction  which 
may  well  be  copied  wherever  and  whenever  possible,  the  resultant 
increase  in  speed  compensating  in  large  degree  if  not  wholly  for  the 
increased  cost  of  construction.  There  are  33  bridges  crossing  high- 
ways and  streams;  the  majority  of  these  structures  have  concrete 
abutments  and  steel  girders.  There  is  one  three-arch  bridge  of 
granite  masonry,  and  one  bridge  using  steel  girders  supported  upon 
high  masonry  piers.  The  track  rail  is  a  Boston  &  Albany  section, 
weighing  95  Ibs.  to  the  yard  and  is  supported  upon  8-ft.  ties  spaced 
to  24-in.  centers.  Every  fifth  tie  is  9  ft.  long,  the  extended  ends  of 
these  ties  carrying  the  insulators  which  support  the  contact  rail. 
Tke  ties  are  laid  upon  a  bed  of  anthracite  coal  cinders  topped  with 
a  dressing  of  broken  stone.  All  curves  are  carefully  compounded, 
and  the  outer  rail  properly  elevated  with  reference  to  high  speed 
service. 

The  contact  rails  are  60  ft.  in  length  and  weigh  80  Ibs.  per  yard. 
•The  specified  composition  of  the  contact  rail  is  as  follows : 

Carbon  not  to  exceed  .10  per  cent;  manganese,  .55  per  cent; 
phosphorus,  .OS  per  cent;  sulphur,  .10  per  cent;  silicon,  .03  per 
cent.  Its  conductivity  is  equivalent  to  pure  copper  having  about 
one-eighth  its  cross-section.  The  center  line  of  the  contact  rail  is 
28  ins.  from  gauge  line  of  the  track,  and  its  upper  face  is  5  ins. 
above  the  track  rail,  this  location  being  selected  to  permit  operation 
of  steam  locomotives  over  the  track  without  disturbance  of  the 
contact  rail  or  its  guard.  Fig.  3  shows  relative  position  of  the 
track  rails,  contact  rail,  the  rail  guard  and  collecting  shoe. 

Each  60-ft.  length  of  the  contract  rail  is  anchored  at  its  middle 
by  a  projection  of  the  malleable  iron  casting  at  the  top  of  the 
insulator,  which  projection  engages  with  a  slot  in  the  base  of  the 
rail.  To  allow  for  expansion,  adjacent  rails  are  separated  by  a  dis- 
tance of  1/4-in.  when  temperature  of  the  rail  is  60  deg.  F.  To 
permit  free  expansion  and  contraction,  the  fish  plates  are  left 
sufficiently  loose.  Contact  rail  and  track  rails  are  electrically  con- 
nected throughout  their  respective  lengths  by  copper  bonds  which 
are  soldered  to  the  rails.  These  bonds  are  fastened  under  the  base 


ST1LLWELL:      WILKESBARRE  d  HAZELTON  RAILWAY.       193 

of  the  rail.  The  rail  guard  is  a  2-in.  pine  plank,  6  ins.  in  width, 
supported  directly  over  the  rail  by  oak  posts  at  intervals  of  8  ft., 
these  posts  in  turn  being  supported  by  the  contact  rail  to  which 
they  are  attached  by  means  of  malleable  iron  castings  and  hook 
bolts,  as  shown  in  Fig.  3. 

The  schedule  provided  for  in  the  equipment  of  the  road  con- 
templated an  hourly  express  service  and  a  local  service  upon  "head- 
way of  90  minutes.  The  rolling  stock  equipment  comprises  six 
combination  coaches,  each  having  a  passenger  compartment,  a 


FIG.  3.  — CONTACT  SHOE  AND  GUARD-BAIL. 

baggage  compartment  and  a  toilet-room.  The  passenger  com- 
partment provides  38  seats  of  standard  Pennsylvania  passenger 
car  size,  i.  e.,  40  ins.  long ;  while  eight  seats  are  provided  in  the  bag- 
gage compartment,  which  is  also  used  as  a  smoking  compartment. 
The  general  dimensions  of  the  car  are:  Length  over  end  panels, 
43  ft.;  over  platform,  51  ft.;  width  over  outside  sheathing,  9  ft. 
6  ins. ;  height  from  bottom  of  sill  over  roof,  9  ft.  8-1/2  ins.  Double 
sliding  doors  are  used  at  the  passenger  end  of  the  cars  and  single 
sliding  doors  at  the  opposite  end.  Loading  steps  are  used  at  only 
one  side  of  each  platform,  and  the  side  of  the  platform  opposite 

ELEC.  RYS. —  13. 


194      8TILLWELL:     WILKESBARRE  &  HAZELTON  RAILWAY. 

these  steps  is  used  for  the  motorman's  cab.  At  each  side  of  the 
baggage  compartment  is  a  sliding  door  42  ins.  wide;  the  vestibule 
side  doors  are  hinged  to  the  vestibule  post  next  the  car  body,  and 
when  closed  are  locked  by  the  trap  door  which  is  lowered  to  com- 
plete the  floor  of  the  vestibule  and  cover  the  steps  when  the  door 
is  closed. 

The  cars  are  equipped  with  M.C.B.  couplers,  Gould  platforms 
and  two-stem  spring  buffers.  Automatic  air  sand  boxes  are  used. 
"  Cow-catchers  "  attached  to  the  trucks  are  placed  at  each  end  of 
the  car  and  are  set  back  a  sufficient  distance  to  avoid  interference 
with  the  couplings. 

Brill  No.  27-E-2  trucks  are  used;  the  wheel  base  is  7  ft.  6  ins.,, 
and  the  wheels  are  36  ins.  in  diameter.  A  General  Electric  No.  66 
motor  is  attached  to  each  of  the  four  axles.  The  control  system  is- 
the  Sprague  multiple  unit  automatic  control,  using  contactors  in- 
stead of  control  cylinders.  The  total  weight  of  the  car  equipped, 
without  passengers,  is  84,000  Ibs.  A  railway  using  cars  of  this 
weight  and  operating  over  gradients  of  3  per  cent  ranging  from 
3  to  5  miles  in  length,  requires  a  reliable  brake  equipment.  In  the 
case  described  in  this  paper,  both  outside  and  inside  brake  shoes  are 
provided,  the  outside  brakes  being  operated  by  two  independent 
means,  viz.,  Westinghouse  automatic  air  apparatus  and  a  vertical 
hand  wheel  located  in  the  motorman's  cab.  The  inside  brakes  are 
operated  by  a  vertical  wheel  in  the  vestibule  through  mechanical 
connection  absolutely  independent  of  that  which  operates  the  out- 
side shoes.  The  failure  of  no  one  element  in  the  brake  equipment, 
therefore,  can  deprive  the  train  crew  of  effective  means  for  check- 
ing the  speed  of  the  car.  In  the  arrangement  of  the  inside  brake 
equipment,  provision  is  also  made  for  the  Newell  magnetic  track 
brake  which,  however,  has  not  yet  been  developed  for  cars  equipped 
with  motors  of  so  large  a  size  as  are  used  in  this  instance. 

The  Westinghouse  air-brake  apparatus  is  so  arranged  as  to  per- 
mit use  of  the  "straight  air  system,"  and  also  of  the  automatic 
system.  The  former,  by  which  air  admitted  by  opening  the  en- 
gineer's valve  operates  directly  upon  the  piston  of  the  braKe 
cylinder,  is  generally  used  for  the  reason  that  it  readily  permits 
graduated  application  of  the  brakes.  At  the  same  time,  the  auto- 
matic is  available  and  is  brought  into  service  at  any  time  by 
reduction  of  the  train-line  pressure. 

The  cars  are  arranged  for  operation  singly  or  in  trains,  the 
multiple-unit  control  system  being  adopted  with  special  reference 


STILLWELL:     WILKESBARRE  d  HAZELTON  RAILWAY.       195 

to  possible  ultimate  operation  of  trains  comprising  two  or  more 
cars  each. 

The  construction  of  the  contact  or  collecting  shoe  is  shown  in 
Fig.  4.  This  design  is  due  to  Mr.  W.  B.  Potter,  chief  engineer  of 
the  railway  department  of  the  General  Electric  Company. 


REAR  ELEV. 

FIG.  4.  —  PLAN  OF  THIED-BAIL  SHOE. 


The  cars  are  equipped  with  trolley  poles  for  use  in  passing  over 
portions  of  the  city  traction  systems,  and  the  switch  which  con- 
trols the  connection  to  trolley  and  shoe  is  arranged  to  permit 
change  from  trolley  to  third-rail  supply  or  vice  versa,  without  los- 
ing contact. 

There  are  perhaps  no  special  features  of  the  power  plant  to 
justify  a  detailed  description  in  this  paper.  It  is  located  about 
8.4  miles  from  the  Hazleton  end  of  the  line  upon  Nescopeck  creek. 
The  dimensions  of  the  building  are  132  ft.  x  84  ft. 

The  electrical  equipment  comprises  three  400-kw  three-phase  al- 
ternators of  the  revolving-field  type,  direct-connected  to  three 
single-expansion  twin  engines,  operating  at  150  r.p.m.  Each  en- 
gine has  two  cylinders  18  ins.  in  diameter  and  36  ins.  stroke,  the 
cranks  being  connected  90  deg.  apart  for  the  purpose  of  ob- 


19G      STILLWELL:     WILKESBARRE  d  HAZELTON  RAILWAY. 

taining  uniformity  of  rotation.  Fly-wheels,  15  ft.  in  diameter 
and  weighing  60,000  Ibs.  each,  further  facilitate  parallel  opera- 
tion, and  assist  the  engines  in  taking  care  of  sudden  variations  of 
the  load. 

The  alternators  deliver  tri-phase  currents  at  390  volts.  A  400- 
kw  converter,  located  in  the  power-house,  receives  alternating 
current  from  the  generator  bus  bars,  and  delivers  continuous  cur- 
rent at  about  625  volts  to  contact  rail  where  the  line  passes  the 
power-house. 

Two  groups,  each  comprising  three  transformers  of  150  kw  each, 
connected  in  delta,  deliver  to  the  transmission  circuits  energy  at 
15,000  volts  potential.  The  transformers  are  of  the  oil-insulated 
self-cooling  type.  The  equipment  of  switch  gear  and  measuring 
instruments  present  nothing  worthy  of  special  description. 

At  a  distance  of  11  miles  from  the  power-house,  in  the  direc- 
tion of  Wilkesbarre,  a  sub-station  with  electrical  equipment,  com- 
prising three  step-down  transformers  and  one  400-kw  converter,  is 
located.  The  contact  rail,  from  this  point  to  the  Wilkesbarre 
terminus,  is  supplied  from  this  sub-station,  while  between  the 
sub-station  and  power-house  it  is  supplied  at  each  end  from  the 
converters  located  at  these  points.  At  the  Hazleton  end  of  the 
line,  which  is  8.4  miles  from  the  power-house,  the  contact  rail 
is  supplied  in  part  from  the  power-house  of  the  Lehigh  Traction 
Company,  the  direct-current  compound-wound  generators  in  the 
plant  of  that  company  operating  in  parallel  with  the  rotary  con- 
verter at  the  power-house  of  the  Wilkesbarre  &  Hazleton  Railway. 

The  alternating-current  transmission  from  power-house  to  sub- 
station —  and  to  a  point  several  miles  beyond  the  latter  —  em- 
ploys a  potential  of  15,000  volts.  The  circuit  comprises  three 
bare  copper  wires,  No.  4  B  &  S  gauge,  forming  an  equilateral  tri- 
angle 30  ins.  on  each  side.  Double-petticoat  glass  insulators 
7  ins.  in  diameter  are  used.  The  poles  are  spaced  100  ft.  on 
curves  and  125  ft.  on  tangents.  Locust  pins  7  ins.  long  and 
2  ins.  in  diameter,  where  they  enter  the  cross-arm,  are  used. 
Two  of  the  pins  are  carried  by  the  cross-arm,  and  the  third  is  in- 
serted in  the  top  of  the  pole,  which  is  clamped  with  7-in.  iron 
bands.  The  yellow-pine  cross-arms  are  6  ins.  x  4r|  ins.  in  section 
and  34  ins.  long.  They  are  secured  to  the  pole  by  two  5/8  in.  bolts. 
The  transmission  circuit  is  transposed  twice,  each  transposition 
making  one-third  of  a  turn. 


STILLWELL:     WILKESBARRE  d  HAZELTON  RAILWAY.       197 

The  transmission  circuit  is  carried  to  a  distance  of  14  miles 
from  the  power-house  in  the  direction  of  Wilkesbarre,  i.  e.,  about 
three  miles  beyond  the  fixed  sub-station  at  Nuangola.  This  is 
done  to  permit  the  supply  of  alternating  current  to  the  portable 
sub-station,  which  is  sometimes  located  at  the  end  of  the  trans- 
mission circuit. 

The  portable  sub-station  comprises  a  car  36  ft.  long  and  9  ft. 
6  ins.  wide,  carrying  a  complete  sub-station  equipment  of  electrical 
apparatus,  comprising  three  150-kw  transformers,  one  400-kw 
converter,  and  a  complete  outfit  of  alternating-current  and  con- 
tinuous-current switching  apparatus.  It  is  also  equipped  with 
lightning  arresters  and  reactance  coils.  Fig.  5  illustrates  the 
arrangement  of  the  apparatus  inside  the  car.  The  total  weight 
of  the  equipment  is  about  51,000  Ibs.  The  car  is  not  equipped 
with  motors;  but,  when  necessary,  is  .attached  to  a  regular  passenger 
car  and  hauled  to  any  part  of  the  line  where  it  may  be  needed. 
In  the  operation  of  the  line  it  serves  the  double  purpose  of  pro- 
viding a  reserve  for  the  transforming  and  converting  equipment 
of  the  power-house  and  sub-station,  and  of  supplying  an  additional 
sub-station,  which  may  be  located  near  the  top  of  the  long  grade 
at  the  Wilkesbarre  end  of  the  line  when  traffic  on  that  part  of 
the  system  is  particularly  heavy,  as  may  happen  in  case  of  special 
excursions  from  the  city. 

EXPERIENCE  IN  OPERATION. 
1).  The  Contact  Rail  Guard. 

In  operation  of  the  road  the  guard  has  repeatedly  demonstrated 
its  value  in  protecting  the  contact  rail  against  sleet  and  thereby 
preventing  interruptions  of  service,  which  in  the  severe  winter 
climate  of  these  Pennsylvania  mountains  would  otherwise  have 
been  comparatively  frequent  and  serious.  During  the  winter  of 
1903-04  cars  were  operated  from  6  a.  m.  until  midnight  upon  head- 
way which  at  no  time  was  less  than  one  hour,  and  notwithstanding 
this  infrequent  service  and  the  fact  that  no  cars  were  running 
between  midnight  and  6  a.  m.  there  were  but  two  instances  in  which 
any  serious  delay  occurred  by  reason  of  the  formation  of  sleet  on 
the  contact  rail.  Upon  one  occasion  a  car  was  delayed  one  hour  and 
50  minutes,  and  at  another  time  a  car  lost,  during  the  round  trip, 
28  minutes.  The  trouble  occurred  on  a  stretch  of  track  where  the 


198      STILL  WELL;     WILKESBARRE  &  HAZ ELTON  RAILWAY. 


FIG.  5.  —  CONVERTER  CAB. 


STILLWELL:     WILKESBARRE  d  HAZELTON  RAILWAY.       199 

line  is  particularly  exposed  to  the  sweep  of  the  wind  over  the  moun- 
tains. Partial  formation  of  sleet  on  top  of  the  contact  rail  which 
occurred  in  these  cases  would  have  been  greatly  reduced,  if  not 
eliminated,  had  the  guard  been  even  2  ins.  wider.  In  cases 
where  it  is  not  necessary  to  consider  the  possibility  of  occasional 
operation  of  steam  rolling  stock  experience  on  this  road  seems  to 
show  that  effective  protection  against  sleet  can  be  secured  by  em- 
ploying a  horizontal  plank  guard  substantially  as  shown  in  Fig.  3, 
but  extended  in  each  direction,  i.  e.,  toward  the  track  and  away 
from  it  1  in.  farther  than  the  guard  adopted  in  this  instance. 
Where  possible  operation  of  steam  rolling  stock  will  not  permit 
Mich  extension  in  the  direction  of  the  track,  the  guard  should  be 
widened  at  least  1  in.  in  the  other  direction,  i.  e.,  away  from 
the  track. 

The  addition  of  a  vertical  plank  attached  to  the  posts  which  carry 
the  top  guard  would  secure  effective  protection  against  sleet  com- 
ing from  that  side  of  the  track,  but  on  the  other  hand  it  would 
tend  to  cause  the  accumulation  of  snow  around  and  upon  the 
contact  rail.  Mr.  C.  B.  Houck,  superintendent  of  motive  power 
of  the  Wilkesbarre  &  Hazleton  Railway,  to  whose  courtesy  I  am 
indebted  for  many  particulars  regarding  operation,  attributes  the 
success  of  the  guard  in  large  degree  to  the  fact  that  it  is  open  front 
and  back,  so  permitting  the  wind  to  drive  snow  through  the  space 
between  contact  rail  and  the  guard. 

2).  The  Collecting  Shoe. 

The  use  of  a  horizontal  guard  above  the  contact  rail  implies 
necessarily  the  adoption  of  a  collecting  device  differing  from  the 
familiar  link  type  generally  employed  in  connection  with  systems 
of  third-rail  supply.  On  the  whole,  experience  in  operation  of  the 
shoe  illustrated  in  Fig.  3  has  been  very  satisfactory,  and  in  the 
opinion  of  the  writer  has  demonstrated  the  essential  superiority  of 
a  shoe  of  this  type,  particularly  at  high  speeds.  Some  trouble  in 
breaking  shoes  has 'resulted  from  failure  to  maintain  accurate 
alignment  of  contact  rail  and  track  rails,  as  a  consequence  of  which 
shoes  have  been  broken  by  striking  against  the  posts  which  support 
the  guard,  and  in  order  to  make  sure  that  when  the  shoe  strikes 
these  posts  the  break  shall  occur  nt  a  predetermined  point  and  not 
carry  away  the  supporting  casting  as  well  as  the  shoe,  it  has  been 
deemed  advisable  to  reduce  the  section  of  the  shoe  casting  at  the 


200      STILLWELL:     WILKESBARRE  d  HAZELTON  RAILWAY. 

weakest  point  to  the  dimensions  shown  in  Fig.  4,  which  in  this  re- 
spect are  considerably  modified  as  compared  with  the  original 
design.  At  high  speeds  the  shoe  has  less  tendency  to  jump  than  the 
link  type  shoe,  the  moving  parts  being  comparatively  light,  and 
the  spring  pressure  —  about  15  Ibs. —  proving  more  effective  than 
gravity  in  maintaining  contact  of  shoe  and  rail.  The  design  of  this 
shoe  can  with  advantage  be  materially  modified  in  respect  to  details ; 
in  type,  however,  it  is  excellent  and  very  satisfactory. 

Its  ability  to  collect  heavy  currents  satisfactorily  was  well  dem- 
onstrated by  a  test  carried  out  for  the  purpose  of  determining  the 
ability  of  the  electrical  equipment  of  the  Wilkesbarre  &  Hazleton 
cars  to  draw  a  heavy  trail  car  up  the  mountain  grades.  In  this 
test  a  motor  car  was  coupled  to  a  standard  Lehigh  Valley  passenger 
coach  weighing  70,000  Ibs.  The  total  weight  of  the  two-car  train, 
including  train  crews  and  observers  reading  the  measuring  instru- 
ments, was  156,000  Ibs.  Simultaneous  readings  of  current  and 
o.m.f.  were  taken  at  30-second  intervals  at  the  power-house  and 
at  the  permanent  sub-station,  and  similar  readings  were  taken  at 
15-second  intervals  on  the  motor  car.  At  times  the  speed  was 
determined  with  a  fair  degree  of  accuracy  by  counting  rail  joints, 
although  at  the  higher  speeds  the  results  thus  obtained  are  hardly 
reliable. 

The  start  was  made  at  the  Wilkesbarre  terminal  at  1  a.  m.,  and 
the  run  to  the  Hazleton  end  of  the  line  was  accomplished  in  68 
minutes,  the  average  speed  being  22  miles  per  hour.  During  this 
run  the  current  per  motor  cars  in  climbing  the  long  3  per  cent 
grades  exceeded  400  amperes  per  shoe.  The  only  sparking  noted 
occurred  at  irregular  intervals,  averaging  perhaps  distances  of 
something  over  a  quarter  of  a  mile,  and  due  doubtless  to  slight 
differences  in  elevation  of  adjacent  rail  ends.  The  night  was 
dark  and  the  slightest  spark  under  the  shoe  was  easily  detected. 
At  the  end  of  the  run  the  shoes  were  found  to  be  in  good  order 
and  not  excessively  heated. 

3).  The  Brake  Equipm^ent. 

That  the  brake  equipment  of  some  of  our  electrically  operated 
urban,  suburban  and  interurban  lines  is  inadequate  has  been 
demonstrated  in  recent  years  by  a  number  of  fatal  accidents ;  that 
similarly  unsafe  conditions  exist  in  the  equipment  of  many  other 
line?  is  undoubtedly  true.  Electric  traction  is  admirably  adapted 


STILLWELL:     WILKESBARRE  &  HAZELTON  RAILWAY.       201 

to  operation  over  heavy  grades.  Obviously  special  precautions  in 
respect  to  brake  equipment  should  be  observed  where  these  grades 
are  encountered.  The  general  features  of  the  equipment  provided 
in  this  instance  have  been  described.  In  operation  they  have 
proved  very  satisfactory.  Where  both  inside  and  outside  shoes 
are  used  it  is  found  advantageous  in  descending  heavy  grades  ta 
apply  one  set  or  the  other  to  the  point  of  actual  contact  with  the 
wheel,  leave  this  set  thus  adjusted  and  use  the  other  set  for  such 
additional  braking  as  may  be  necessary.  This  method  is  par- 
ticularly advantageous  where  axles  and  trucks  are  light  in  con- 
struction, or  where  from  long  usage  or  inadequate  maintenance 
there  may  be  lack  of  rigidity,  and  where,  consequently,  if  but 
one  set  of  brake  shoes  be  applied  the  braking  may  become  inef- 
fective. The  partial  application  of  one  set,  e.  g.,  the  inside  shoes,, 
holds  the  wheel  firmly  in  place,  and  increases  the  promptness  and 
effectiveness  of  results  attained  in  applying  the  other  set  of  brakes. 
In  the  operation  of  the  Wilkesbarre  &  Ilazleton  Kailway,  when  a 
car  reaches  the  top  of  one  of  the  long  grades  the  conductor  takes- 
his  place  in  the  vestibule  and  applies  the  inside  brakes  by  hand, 
tightening  them  just  sufficiently  to  take  up  the  lost  motion  and 
bring  the  shoes  into  firm  contact  with  the  wheels.  The  motor- 
man  then  holds  the  train,  usually  by  applying  the  air-brake  a& 
may  be  necessary,  and  in  case  any  part  of  the  brake-rigging  of  the 
air-brake  apparatus  should  fail  the  car  can  be  held  by  using  the 
inside  brakes,  which  being  already  in  contact  with  the  wheels 
can  be  promptly  applied. 

4).  The  Converter  Car. 

The  practical  value  of  a  movable  sub-station  has  been  demon- 
strated a  number  of  times  in  service.  It  is  a  sufficiently  effective 
reserve  for  the  converters  located  respectively  in  the  power-house 
and  the  permanent  sub-station  at  Nuangola,  and  it  has  also  been 
used  with  satisfactory  results  to  increase  the  supply  of  continuous 
current  on  the  long  and  steep  grade  which  begins  at  the  Wilkes- 
barre end  of  the  railway. 

The  speed  with  which  the  powerful  motor  equipments  carry  up 
the  long  and  heavy  grades  cars  weighing,  with  their  load,  over 
90,000  Ibs.  each  is  a  striking  illustration  of  the  possibilities  of 
electric  traction  in  railway  work.  Upon  the  occasion  of  the  test 
with  trail  car,  which  has  been  referred  to,  the  speed  of  the  train 


202       STILLWELL:     WILKESBARRE  &  HAZELTON  RAILWAY. 

at  a  point  midway  between  the  power-houses  at  St.  Johns  and  at 
Hazleton  was  28  miles  per  hour,  the  grade  being  3  per  cent,  and  the 
weight  of  the  train  156,000  Ibs.  At  points  nearer  the  power-house, 
the  grade  being  the  same,  the  speed  attained  was  not  less  than  34 
miles  an  hour. 

FRIDAY  MORNING  SESSION,  SEPTEMBER  16. 
CHAIRMAN  DUNCAN:     The  session  this  morning  will  consist  of  a  discus- 
sion, or  a  continuation  of  the  discussion  on  the  application  of  alternate 
motors  to  railway  work,  and,  if  we  have  time,  the  reading  of  a  paper  by 
Mr.  Parke  on  "  Braking." 

DISCUSSION. 

I  will  take  the  privilege  of  opening  the  discussion  myself  with  some  re- 
marks on  the  general  subject  of  the  application  of  electricity  to  railroads. 
In  the  first  place,  the  types  of  service  that  electricity  has  to  perfect  are 
tramway  service,  city- train  service,  interurban  service  and  trunk-line  ser- 
vice. Now,  of  those  types  the  first  three  have  fallen  victims  to  elec- 
tricity—  tramways,  city-train  service  and  interurban  service  are  now 
operated  by  electricity.  The  reason  is,  of  course,  that  electricity  affords 
better  facilities  and  is  cheaper. 

Before  the  road  at  Richmond,  Va.,  was  started  in  1887  and  1888,  the 
practical  success  of  electricity  as  a  motive  power  had  been  shown.  It 
had  been  shown  that  electricity  could  be  applied  to  the  propulsion  of  cars. 
It  had  not  been  shown  that  it  was  practical  commercially.  That  experi- 
ment showed  it  was  commercially  practical,  and  from  that  time  in  tram- 
Avays  the  motive  power  was  rapidly  changed  to  electricity. 

What  happened  in  the  tramway  service  was  this :  A  large  number  of 
small  units  were  operated  from  one  station;  that  means  that  the  load 
factor  at  the  station  was  good;  that  means  that  the  load  factor  on  the 
<?opper  was  good,  and  operated  direct  currents  from  one  or  more  stations 
at  a  time.  When  the  question  of  displacing  cables  came,  the  situation 
was  more  serious.  Cable  traction  was  successful ;  it  was  economical,  and 
for  crowded  districts  it  was  hard  to  see  how  electricity  would  replace  it. 
However,  the  advance  electricity  made  gradually  ousted  cables  from  tram- 
way work. 

For  city-train  service,  again  electricity  ran  against  a  harder  propo- 
sition. The  elevated  roads  were  run  by  steam  locomotives.  The  mechani- 
cal arrangements  and  the  investments  necessary  to  change  to  electric 
traction  were  enormous.  It  was  not  until  the  multiple  system  gave  elec- 
tricity a  decided  advantage  over  steam,  that  electricity  was  adopted  over 
urban  roads.  In  this  city-train  service  we  have  the  same  condition  of 
affairs.  We  have  a  large  number  of  units  in  a  small  compass,  as  in  the 
case  of  the  tramway  work,  and  a  still  larger  number  of  units  on  one  sta- 
tion, a  comparatively  good  load  factor  for  the  station,  a  comparatively 
.good  load  factor  for  the  copper. 

For   interurban   roads  the  advantages   offered  by   electricity   were   very 


STILLWELL:      WILKESBARRE  6  HAZELTON  RAILWAY.     203 

marked.  It  opened  up  a  new  type  of  service  impossible  to  be  operated  by 
steam.  It  gave  to  country  districts,  the  headway  of  the  cars  varying  from 
twenty  minutes  to  an  hour,  a  service  which  it  was  impossible  for  steam  to 
give,  and  the  reason  of  its  development  was  the  fact  that  this  service 
could  be  economically  given.  The  reason  of  that,  again,  was  the  fact  that 
by  successive  distribution  a  large  number  of  units  could  be  fed  from  one 
station.  The  load  factor  on  the  main  station  was  good,  although  the  load 
factor  on  the  sub-stations  and  on  the  copper  was  bad.  The  load  factor  on 
the  sub-stations  and  on  the  distributing  part,  the  transmission  part,  on 
the  copper,  has  been  improved,  of  course,  by  the  use  of  storage  batteries 
in  the  sub-stations. 

Now,  in  all  of  these  cases  the  reasons  for  the  success  of  electricity 
lies  in  the  fact  that  the  load  factor  on  the  generating  station,  where  the 
Josses  are  greatest,  has  been  brought  to  a  reasonable  figure.  The  load 
factor  on  the  sub-stations  is  not  so  important  in  its  effects  because 
losses  in  the  sub-stations  are  not  of  great  importance.  The  load  factor  on 
the  copper  is  of  importance,  dependent  upon  the  amount  of  copper  used  in 
the  distribution  of  the  service  to  the  cars.  The  load  factor  on  the  copper 
i-s  very  bad,  of  course,  but  the  expenditure  for  copper  is  not  great. 

Now,  there  is  another  point  to  be  considered  when  you  come  into  work 
like  steam-railway  service,  and  that  is  this:  The  load  factor  itself,  as  a 
figure,  does  not  tell  the  whole  story  by  any  means.  We  may  have  in  the 
same  station  the  same  load-factor  for  two  days,  and  the  power  per  hour 
may  cost  the  second  day  twice  as  much  as  the  first.  In  the  ordinary  load 
we  have  the  load  curve,  which  gives  us  the  amount  of  power  required  at 
different  times  in  the  day,  and  we  run  our  boilers  and  our  generating 
units,  turning  them  on  as  the  power  increases.  In  the  type  of  load  that 
would  be  given  by  railroad  work,  we  do  not  have  a  curve  that  comes  up  and 
varies  twice  a  day,  but  we  have  a  curve  that  fluctuates  greatly  from  time 
to  time.  So  a  large  part  of  the  capacity  of  the  plant  must  be  used  all 
the  time.  Consequently,  it  is  necessary  to  introduce  another  considera- 
tion, and  that  is  the  cost  factor  of  power.  With  the  same  load-factor,  the 
cost  factor  may  differ  very  much.  If  we  define  the  cost  factor  as  the 
ratio  of  the  actual  cost  per  kilowatt-hour  delivered  to  the  cost  per 
kilowatt-hour  at  full  load,  we  will  find  with  the  same  load  factor  that 
the  cost  factor  will  vary  considerably,  for  if  our  boilers  have  to  be  operat- 
ing and  ready  to  give  steam  at  any  moment,  losses  would  continually  be 
greater  than  if  the  boilers  are  banked  and  fire  spread  only  when  we  need 
power. 

In  the  same  way  the  cost-factor  of  our  copper  varies  with  the  nature 
of  the  load  factor.  If  we  have  a  given  amount  of  energy  to  distribute, 
and  have  enough  copper  to  give  it  10  per  cent,  loss,  if  it  is  distributed 
over  twenty- four  hours,  then  if  we  distribute  the  same  amount  of  energy 
in  twelve  hours,  the  loss  is  twice  as  great.  So  in  any  situation  we  must 
have  determined  the  cost  factor  in  our  copper,  the  cost  factor  in  our 
(sub-station,  if  we  use  one,  and  the  cost  factor  in  the  main  station;  and 
those  are  figures  that  are  more  important  than  load  factors,  and  dependent 
not  only  upon  the  load  factor,  but  also  upon  the  nature  of  the  load  factor. 

When  we  come  to  trunk-line  work,  the  matter  has  been  discussed  and 


204      STILLWELL:     WILKESBARRE  &  HAZELTON  RAILWAY. 

will  be  discussed  further.  Taking  for  granted  the  possibilities  of  single- 
phase  alternating  motors,  taking  for  granted  voltages  which  make  the 
copper  investments  comparatively  small,  we  are  in  the  same  condition 
that  we  are  in  the  other  three  types  of  service.  That  is,  we  can  put  on 
our  generating  station,  where  the  losses  are  greatest,  a  fair  load  factor. 
The  type  of  the  load  factor,  however,  will  be  different  from  the  type  of 
load  factor  in  our  ordinary  service,  and  that  must  be  taken  into  con- 
sideration in  determining  the  cost  of  the  power  to  be  used.  If  we  can  use 
high  voltages  there  is  no  doubt  about  it,  that  we  can  operate  steam 
roads  with  overhead  wires,  the  voltage  being  high  enough  to  bring  the 
current  down  to  the  quantity  that  can  be  collected.  But  the  question  is 
whether  there  is  any  great  advantage  in  it. 

We  have  had  that  fully  discussed,  and  I  hope  we  will  have  it  further 
discussed,  but  it  seems  to  me  this:  We  can  offer  very  little  to  the  gen- 
eral railroad  man,  we  can  offer  very  little  in  the  way  of  decreased  ex- 
pense. We  can  offer  very  little  in  the  way  of  increased  facility  of  opera- 
tion. We  do  offer  them  this,  though:  We  offer  them  the  possibility  of  a 
great  deal  of  trouble  by  using  a  high  tension  distributing  system,  by 
collecting  from  a  high  tension  system  to  feed  our  road  depending  for  its 
operation  upon  a  few  large  units  spaced  at  large  distances;  that  is,  at 
central  stations,  and  then  distributing  through  sub-stations. 

It  seems  to  me,  so  far  as  the  general  problem  goes,  outside  of  special 
problems  that  come  up,  that  we  still  are  not  in  a  position  to  offer  for 
general  railroad  work  any  particular  advantage  of  electricity  over  steam. 
There  are  specific  problems,  as  every  one  knows,  in  which  electricity  has 
tremendous  advantages.  Some  years  ago  I  investigated  for  the  B.  &  0. 
the  electrification  of  a  section  100  miles  in  length,  where  the  steam  con- 
ditions had  become  practically  impossible.  The  road  was  run  up  to  its 
trackage  limit  and  it  curved  so  that  the  heaviest  locomotives  were  limited, 
therefore  the  weight  of  the  locomotive  and  therefore  the  size  of  the  train. 
Dr.  Hutchinson  and  myself  went  through  that  very  carefully,  and  found 
electricity  offered  great  advantages.  There  was  one  grade  of  seventeen 
miles  of  2^  per  cent,  and  another  of  fourteen  at  2^&  per  cent.  In  a  case  of 
that  kind  there  is  no  question  of  considering  the  loss  in  electricity,  but  by 
starting  at  one  end  and  ending  at  the  other  there  is  great  advantage  in 
the  traffic. 

Another  advantage  Mr.  Leonard  pointed  out  is  the  fact  that  electricity 
allows  us  to  increase  the  length  of  train  with  the  steam  draw-bar  con- 
ditions. The  size  of  the  train  is  practically  limited  by  draw-bar  con- 
ditions, and  with  electricity  the  train  can  be  very  much  increased. 

I  think  Dr.  Steinmetz  took  the  ground  that  the  reason  for  the  larger 
train  units  was  the  increased  economy  of  large  locomotives.  That,  of 
course,  is  not  exactly  so.  The  reason  for  the  larger  train  units  is  in  the 
economy  of  the  large  locomotives  and  the  increased  tractive  effort. 

There  is  very  little  that  electricians  to-day,  even  with  the  single-phase 
alternating  motor,  can  offer  to  railroad  people,  except  assistance  in  special 
problems. 

Mr.  F.  J.  SPRAGUE:  Discussion  on  this  subject  seems  to  be  assuming 
two  phases, —  first,  how  to  use  the  alternating  current  in  railway  work, 
and,  second,  whether  trunk  lines  can  be  operated  by  electricity. 


XTILLWKLL:     WILKESBARZE  d  HAZELTON  RAILWAY.      205 

This  will  extend  the  discussion  into  a  pretty  broad  field.  We  can  all 
learn  something  from  the  milestones  we  pass,  and  in  view  of  the  numerous 
claims  which  have  been  made  for  the  alternating-current  motor,  more  par- 
ticularly of  the  single-phase  type,  I  would  recall  some  promises  made  a 
number  of  years  ago  when  the  continuous-current  motor  was  to  be 
promptly  relegated  to  obscurity.  You  all  remember  the  early  phases  of 
the  development  of  the  polyphase  motor,  and  how  the  commutator  was 
held  to  be  the  great  bugbear  of  its  rival.  The  commutatorless  motor 
was  to  institute  a  revolution  in  railway  work.  Of  course  it  has  been 
applied  to  stationary  purposes  most  successfully,  and  two  companies  in 
particular,  the  Ganz  and  Siemens,  have  made  some  effective  demonstra- 
tions of  its  possibilities  in  railway  work. 

I  cannot,  however,  but  feel  that  the  multiplicity  of  conductors  is  a 
practical  bar  toward  any  widespread  application  of  this  system.  The 
position  I  take  is  not  a  new  one.  In  1888,  when  the  question  of  equip- 
ment of  the  West  End  Railway  of  Boston  was  under  consideration,  and 
the  Bell  Telephone  Company  with  all  its  power  attempted  to  prevent  the 
use  of  the  rails  for  return  circuits,  the  president  of  that  road  had  to 
consider  very  seriously  whether  they  would  use  two  trolley  wires.  I 
objected  to  it  as  strongly  as  possible,  and  the  modern  trolley  has  been 
developed  on  the  idea  that  one  wire  overhead  is  quite  sufficient, —  often- 
times too  many,  perhaps. 

And  so,  I  think,  in  the  alternating-current  development,  we  shall  proceed 
on  the  basis  that  one  conductor  overhead  is  all  that  we  can  stand.  If 
the  experiments  made  demonstrate  anything  at  all,  it  is  the  impracti- 
cability of  operating  general  trunk  lines  on  the  polyphase  system. 

Now,  after  all  these  years  and  the  various  promises  that  have  been 
made  on  behalf  of  the  polyphase  type  of  motor,  we  find  in  the  series 
single-phase  motor  a  reversal  of  practice,  and  the  adoption  of  many  of 
the  features  of  continuous-current  motors.  The  much-abused  commutator 
has  reappeared  in  a  more  unsatisfactory  form,  and  the  field  windings  are 
more  complicated.  I  think  I  am  safe  in  saying,  that  not  only  at  present, 
but  for  all  time  to  come, —  prophecies  are  dangerous,  but  I  think  I  will 
stand  pat  on  this  one  —  the  continuous-current  motor,  measured  by  all 
qualities, —  weight,  efficiency,  simplicity,  reliability  and  cost  of  mainte- 
nance, can  claim  superiority  over  the  alternating-current  motor  of  the 
single-phase  type. 

Why,  then,  are  we  striving  for  the  development  of  the  latter  machine? 
It  is  not  because  it  is  necessary  in  street-car  service  or  in  elevated  rail- 
way or  underground  work,  or  for  limited  distances  on  interurban  roads,  but 
to  i  educe  on  long  distances,  and  especially  heavy  traction  the  prime  in- 
vestment for  line  equipment,  and  the  investment  in  the  moving  parts  at 
the  sub-stations. 

Just  here  I  may  point  out  that  people  are  apt  to  somewhat  exaggerate 
the  saving  to  be  effected.  Any  road  which  extends  over  a  considerable 
territory  and  operates  from  sub-stations  may  be  considered  merely  as  a 
series  of  connected  railways  operated  from  small  central  stations,  each  of 
which,  instead  of  being  steam-equipped,  is  run  directly  by  a  current  trans- 
Mi  itted  from  one  central  source.  Increase  the  working  potential  and  the 


206     8TILLWELL:     WILKESBARRE  &  HAZELTON  RAILWAY. 

distance  between  these  small  stations  can  of  course  be  increased.  The 
ordinary  limit  for  continuous  current  work  has  been  primarily  determined 
by  the  limits  of  successful  commutation  for  a  single  motor,  but  by  operat- 
ing two  in  series  on  four  motor  equipments  the  limit  can  be  at  once 
doubled, —  to  say  nothing  of  other  possibilities.  When  we  put  an  alter- 
nating current  directly  upon  the  working  conductor  we  run  into  certain 
possible  difficulties.  In  the  first  place,  the  distance  between  the  stations 
cannot  be  increased  in  that  ratio  which  at  first  sight  would  appear. 
Whatever  the  maximum  limit  on  the  trolley  wire,  the  average  potential 
is  of  course  much  less,  and  the  resistance  of  iron  rails  to  the  passage 
of  an  alternating  current  is  much  higher  than  for  the  continuous.  It  can 
be  safely  said  that  with  any  given  size  of  trolley  wire,  and  average  load  per 
unit  distance,  the  distance  between  the  sub-stations  on  an  alternate- 
current  proposition  would  not  by  any  possibility  increase,  in  the  same 
ratio  as  the  increase  of  maximum  potential,  when  compared  with  con- 
tinuous-current equipment,  nor  even  directly  as  the  ratio  of  increase  of 
its  own  potential,  alternating-current  propositions  alone  being  considered. 

In  the  operation  of  a  single-phase  alternating-current  motor  I  fear 
that  we  have  not  passed  through  that  period  of  time,  or  those  conditions 
of  service,  which  will  develop  certain  conditions,  some  possibly  dangerous 
and  some  irritable.  In  the  earlier  days  of  electric  railroading  probably 
most  of  us  have  at  times  noticed  the  possibility  of  shock, —  and  that  with 
only  400  or  500  volts, —  due  to  leakages  on  the  car  and  a  break  between 
the  metal  of  the  car  and  the  rails  or  the  ground,  when  a  passenger  on 
moist  ground  made  a  contact  in  taking  hold  of  the  handrail.  That  ex- 
perience leads  to  a  possibility  in  high  tension  work  which  is  not  entirely 
agreeable  to  contemplate,  and  against  which  the  utmost  precaution  must 
be  taken. 

We  must,  if  we  are  going  to  have  high-tension  transmission  on  the  trolley, 
bring  that  high  tension  into  the  car.  It  matters  not  whether  we  are 
going  to  use  high  tension  direct  on  the  motor  circuit,  or  whether  we  are 
going  to  use  a  transformer  and  reduce  it,  the  high  tension  must  come  in 
somewhere.  This  high-tension  alternating  circuit  has  a  greater  tendency 
to  break  down  insulation,  and  it  must  of  course  be  protected  by  an  iron  or 
lead  shield  which  must  be  put  in  connection  with  the  metal  frame  of  the 
car.  In  time  the  gradual  deterioration  of  the  insulation  may,  in  fact,  it 
most  likely  will,  lead  to  a  partial  or  perhaps  a  complete  break-do wn,. 
bringing  the  whole  metal  frame  into  potential  relation  with  the  incoming 
current. 

Fortunately,  in  most  propositions  for  alternating-current  work  heavy 
cars  are  used  which  most  of  the  time  will  make  good  rail  contact,  but 
we  can  easily  see  that  at  times  on  dirty  or  sleety  tracks  there  may  arise  a 
condition  in  which  there  is  a  decided  difference  of  potential  between  the 
frame  of  the  car  and  the  ground.  That  leads  to  possible  dangerous  con- 
ditions, and  will  require  the  utmost  care  on  the  part  of  engineers  who 
are  installing  electric  equipment  on  alternating-current  circuits. 

There  is  another  condition  to  be  considered.  Fifty  times  a  second  the 
potential  passes  zero,  and  current  ceases.  When  running  with  a  con 
tinuous  current,  circuit  can  often  be  maintained  even  through  bad  rail 


STILLWELL:     WILKESBARRE  d  HAZELTON  RAILWAY.      207 

contacts,  but  under  this  latter  condition  there  seems  a  liability  of  a 
greater  aggregate  period  of  interruption  of  current  in  an  alternating-cur- 
rent equipment  than  there  is  on  the  continuous  current. 

The  question  whether  electricity  should  be  used  on  trunk  lines  is  such  a 
big  one  that  discussion  would  be  almost  endless.  As  the  chairman  has 
pointed  out,  there  are  special  conditions,  such  as  characterize  sections  of 
mountain  roads  and  terminals, —  where  electricity  should  be  seriously  con- 
sidered; and  there  are  certain  congested  conditions  on  some  railroads,  and 
especially  some  of  the  foreign  lines,  where  it  is  almost  impossible  to  ex- 
tend terminal  facilities,  which  call  for  electric  operation.  But,  as  I  stated 
at  the  general  meeting  of  the  Congress  the  other  day,  I  think  that  a  great 
deal  of  the  money  which  may  be  available  to  a  trunk-line  system  would 
be  often  spent  in  protecting  its  territory  rather  than  changing  equipment. 

When  the  electric  railroad  was  first  introduced,  of  course  everybody 
sought  franchises.  Many  people  got  them,  and,  as  usual  in  this  country, 
at  a  very  low  cost.  They  have  often  pre-empted  the  territory  parallel  to 
steam  railroads,  have  created  a  business  of  their  own,  and  are  in  position 
to  divert  business  from  the  steam  roads.  As  such  they  are  commercial 
propositions  which  can  very  easily  be  investigated,  and  no  one  should  be 
better  qualified  to  investigate  these  propositions  than  the  steam  railroad 
owners  and  managers.  If  I  had  a  railway  running  between  two  points, 
with  termini  and  roadbed  well  established,  and  somebody  built  a  road 
alongside  of  me, —  it  matters  not  whether  steam  or  electric, —  and  created 
a  special  business  besides  diverting  my  traffic,  I  would,  if  I  could  on  fair 
terms,  get  control  of  it.  I  would  not  try  to  duplicate  a  special  traffic  on  a 
system  that  was  not  fitted  for  it.  And  so  I  think  that  the  policy  which  1 
see  by  the  public  press  is  being  more  or  less  adopted  by  the  New  York 
Central  and  some  other  railroads  of  buying  up  properties  adjacent  to  them, 
which  cannot  be  duplicated  and  which  have  already  created  business  of 
their  own,  is  one  which,  commercially  speaking,  is  by  long  odds  one  of 
the  best  things  the  trunk  line  management  can  do. 

In  foreign  countries,  where  there  is  not  that  freedom  of  granting  fran- 
chises, and  where  the  local  conditions  do  not  permit  quite  that  interurban 
service  that  we  have  here,  necessity  dictated  by  competition  is  of  course 
less,  but  the  congestion  of  roads  that  terminate  in  cities  like  London  is 
creating  special  conditions  calling  for  a  change  of  equipment. 

A  good  many  people,  noting  that  the  Pennsylvania  and  the  New  Yora 
Central  systems  are  adopting  electricity  in  New  York,  have  jumped  to  the 
conclusion  that  this  meant  the  end  of  steam  on  trunk  lines.  It  distinctly 
docs  not.  The  Pennsylvania  road  had  to  get  into  the  city  of  New  York 
and  connect  through  to  New  England  and  Long  Island.  There  was  no 
possible  way  save  to  go  underground,  and  the  only  way  they  could  then 
handle  their  trains  successfully  was  by  electricity,  irrespective  of  cost  — 
that  was  a  matter  of  secondary  consideration.  It  does  not  follow  that  the 
Pennsylvania  is  going  to  extend  electricity  on  all  its  trunk  lines,  and  it 
won't  do  it  for  a  good  many  years. 

The  New  York  Central  is  somewhat  similarly  situated.  It  enters  Nev 
York  city  through  a  tunnel.  A  terrible  disaster  in  which  a  number  of 
people  lost  their  livea  focussed  upon  the  road  an  expression  of  public 


208      STILLWELL:     WILKESBARRE  &  HAZELTON  RAILWAY. 

opinion  which  could  not  be  answered  except  in  one  way  —  prompt  assent  to 
legislation  that  steam  road  power  should  be  abandoned ;  and  when  the  deter- 
mination was  made  to  abandon  it,  it  could  not  be  limited  in  territory  to 
that  required  by  law.  To  make  this  clear  I  will  repeat  details  given  at 
another  session.  Most  of  you  know  that  Manhattan  proper  is  bounded 
on  the  north  by  the  Harlem  river,  only  a  few  miles  from  the  main  terminal 
at  Forty-second  Street.  Some  distance  above  this  the  trains  of  the  main 
and  Harlem  divisions,  as  well  as  the  trains  of  the  New  York,  New  Haven 
&  Hartford  lines,  converge,  and  come  into  the  main  station  over  the  New 
York  &  Harlem  Railroad.  It  was  simply  impossible  to  stop  equipment  on 
this  stem.  Furthermore,  in  adopting  electricity  it  was  also  important  to 
consider  not  onb  the  requirements  of  the  law  but  the  effect  upon  suburban 
service,  and  also  upon  the  general  service  in  the  same  territory.  The  terri- 
tory to  be  at  present  operated  and  the  system  to  be  adopted  were  matters 
of  grave  debate.  The  propositions  made  by  the  various  companies,  which 
included  both  continuous  and  alternating-current  work,  had  to  be  carefully 
considered.  The  great  expense  of  electrification  beyond  the  actual  legal 
requirement,  at  a  time  when  all  railway  properties  were  at  a  low  ebb  in 
their  finances,  was  a  serious  one,  so  we  finally  settled  it  something  after 
this  fashion:  The  law  said:  "You  must  abandon  steam."  The  alter- 
native of  course  was  electricity.  "  You  must  go  beyond  the  tunnel."  Going 
beyond  the  tunnel  took  us  to  the  neck  of  a  bottle,  and  we  had  to  get  out 
of  it.  Suburban  lines  were  being  electrified,  and  outlying  competition  was 
ahead.  Great  elevated  and  underground  railroads  existed,  and  the  possible 
relation  of  their  traffic  to  that  of  the  Central  must  be  considered.  So  we 
decided  that  in  the  first  place  we  would  have  to  go  above  the  Harlem  river 
somewhere,  and  then  came  the  question  of  location  of  terminals ;  and  these 
had  to  be  considered  with  relation  to  the  balance  of  the  traffic  of  the  rail- 
road—  long  distance  as  well  as  suburban  traffic, —  and  also  in  connection 
with  property  and  geographical  conditions. 

It  was  finally  decided  that  all  suburban  service  within  a  radius  of  an 
hour's  run  from  New  York,  this,  fortunately  corresponding  to  the  best 
terminal  possibilities,  should  be  made  electric;  and  when  that  was  decided 
it  was  only  reasonable  to  abandon  the  idea  of  maintaining  two  services 
and  three  sets  of  terminals  on  the  same  tracks  in  the  same  territory,  and 
logic  required  that  all  through  trains  within  that  district  should  be  like- 
wise handled  in  the  same  manner. 

The  two  problems  were  somewhat  different,  of  course.  The  result  was 
finally  an  agreement  that  for  a  distance  of  about  twenty-five  miles  on  the 
Harlem  division,  and  for  about  thirty-five  miles  on  the  main  line,  electricity 
should  be  used.  And  these  decisions,  let  me  say,  gentlemen,  have  no  bear- 
ing whatever  upon  what  may  be  done  beyond  these  points  in  the  future ;  nor 
will  anything  that  is  done  in  the  future,  nor  any  development  which  takes 
place  alter  in  my  mind  the  wisdom  of  the  decision  which  has  already 
been  made.  In  fact,  no  other  decision  was  practicable  at  the  time.  There 
was  not  a  company  in  the  world  prepared  at  that  time  to  do  anything  else 
than  supply  continuous-current  motors  to  perform  the  service  which  would 
be  required  by  a  road  where  700  train  movements  a  day  must  be  maintained 
without  excuse,  delay,  or  explanation. 


STILLWELL:     WILKESBARRE  d  HAZELTON  RAILWAY.      209 

SECRETARY  ARMSTRONG:  Mr.  Sprague  touched  on  one  point  to  which  I 
would  like  to  call  attention  to,  and  that  is  the  safety  on  an  ordinary  tram 
car  having  a  potential  on  its  trolley  of  2000  volts  or  more,  and  I  would 
ask  Mr.  Lamme  or  Mr.  Lincoln  if  they  have  anything  to  say  in  connection 
with  this  point. 

Mr.  LAMME:  There  are  several  points  brought  up  in  Mr.  Sprague's 
discussion  of  this  subject  on  which  I  would  like  to  speak  further.  He 
intimates  that  in  a  number  of  ways  the  direct-current  motor  will  always 
be  superior  to  the  alternating-current  motor.  There  is  one  point  in  which 
the  alternating-current  motor  will  be  superior  to  the  direct-current  motor, 
and  that  is  in  the  voltage  which  can  be  utilized  directly  on  the  motor.  The 
direct-current  railway  motor  will  always  necessarily  be  a  high-voltage 
machine.  We  cannot  use  200  or  250  volts  advantageously  on  railway 
service  with  direct-current  motors,  but  we  can  use  it  on  the  alternating 
motors,  because  with  the  alternating  current  we  have  a  simple  means 
of  transforming  the  voltage  from  that  supplied  by  the  trolley  to  whatever 
is  necessary  for  the  motors.  The  high  voltage  on  the  direct-current  railway 
motor  is  a  source  of  weakness  in  practice,  and  in  this  particular  point 
the  alternating-current  motor  wound  for  low  voltage  will  be  superior. 

There  is  a  second  point  of  superiority  in  the  use  of  such  motors  when 
operated  fr»m  a  transformer  on  the  car,  viz.,  by  means  of  a  certain  arrange- 
ment of  the  taps  on  the  transformer,  we  can  reduce  the  maximum  voltage 
from  the  motor  to  the  ground  to  one-half  that  used  on  the  motor.  For 


250V. 


example  let  us  consider  an  arrangement  of  transformer  and  motor  as 
illustrated  in  diagram  No.  1.  Connecting  a  250-volt  motor  across  the 
secondary  of  this  transformer  we  get  from  motor  to  ground  a  maximum 
stress  of  250  volts;  but  if  the  ground  terminal  of  the  transformer  is 


Tr. 


250V. 
I    /JoRv^x 
Gr. 


tapped  at  a  point  midway  between  the  two  secondary  terminals,  as  il- 
lustrated in  the  second  diagram,  then  we  get  125  volts  maximum  to  the 
ELEC.  RYS. —  14. 


210      8TILLWELL:     WILKESBARRE  d  HAZELTON  RAILWAY. 

ground.  With  this  arrangement  with  two  motors  in  series  for  500  volts, 
we  would  get  250  volts  to  the  ground  instead  of  500  as  with  direct  cur- 
rent. This  illustrates  one  of  the  advantages  which  can  be  obtained  by  the 
alternating-current  motor  over  the  direct-current,  and  it  will  serve  to 
eliminate  considerable  trouble  due  to  break-down  of  the  insulation  on  the 
motor. 

In  regard  to  the  difficulties  which  we  will  find  in  the  development  of 
the  single-phase  alternating-current  system,  I  would  say  that  we  are  not 
starting  in  under  the  same  conditions  as  Mr.  Sprague  encountered  in  his 
Richmond  line  and  his  other  early  roads.  At  that  time  comparatively 
nothing  was  known  about  proper  designs  of  railway  apparatus  and  there 
was  practically  no  experience  to  fall  back  upon.  But  the  alternating 
motor  now  comes  at  a  time  when  we  have  had  many  years  of  experience 
in  electric  railway  work,  and  this  is  going  to  make  a  great  difference  in 
the  development  of  the  single-phase  system.  If,  for  example,  in  1887  or 
1888,  we  had  undertaken  the  design  of  the  large  alternators  of  the  Man- 
hattan system  of  New  York  city,  we  would  have  had  an  undertaking  which 
it  would  have  been  practically  impossible  to  carry  through  at  that  date. 
But  at  the  present  time  we  are  ready  and  willing  to  undertake  generating 
machinery  of  much  greater  difficulty  than  the  Manhattan  generators.  In 
the  same  way,  the  alternating-current  motor  now  comes  at  a  time  when  we 
have  had  all  these  years  of  experience  on  railway  work,  and  we  will  be 
able  to  avoid  a  great  many  difficulties  which  developed  in  the  direct-current 
railway  system  and  which  took  years  of  experience  to  find  out  and  eliminate. 

As  to  the  question  of  danger  from  high-tension  trolley  lines,  I  think  it 
will  be  found  to  be  true  that  there  would  be  a  greater  possibility  of  open 
circuits  and  of  shocks  on  a  250-volt  direct-current  railway  circuit,  for 
instance,  than  from  a  500-volt  circuit,  because  the  higher  voltage  is  more 
liable  to  break  through  from  the  car  to  the  ground  and  thus  ground  the 
frame  of  the  car.  With  2000  or  3000  volts,  I  think  it  will  be  almost  im- 
possible to  break  the  circuit  between  the  frame  of  the  car  and  the  ground, 
because  such  voltages  will  spark  through  any  ordinary  separating  or  in- 
sulating medium  on  the  track,  and  thus  close  the  circuit.  In  other  words, 
the  higher  the  voltage  from  trolley  to  ground,  the  less  liable  is  the  circuit 
to  be  opened  between  the  car  and  the  ground. 

There  is  one  point  which  has  not  been  brought  out  before  in  these  dis- 
cussions, which  may  have  important  bearing  on  the  application  of  alter- 
nating-current motors  to  city  work.  A  statement  was  made,  in  one  of  the 
discussions,  that  the  cities  would  probably  maintain  direct  current  for  their 
service,  and  that  the  field  of  the  alternating-current  motor  would  be  in 
suburban  service.  If  you  look  at  only  one  part  of  the  problem  that  might 
appear  to  be  true,  but  there  are  certain  conditions  which  may  be  of  great 
future  importance  in  deciding  this  question.  One  of  these  features,  of 
which  nothing  has  been  said  in  these  discussions,  and  which  may  have 
a  great  deal  of  influence  some  day,  is  the  question  of  electrolysis.  This 
question  has  come  up  in  a  number  of  cases  and  we  know  that  railway  people 
are  thinking  about  it.  It  may  be  a  serious  question  some  day  in  the  cities. 
We  have  made  some  elaborate  tests  to  determine  the  electrolytic  action 


8TILLWELL:     WILKESBARRE  d  HAZELTON  RAILWAY.      211 

of  alternating  currents,  and  while  these  tests  have  shown  that  the  alter- 
nating current  has  a  slight  action,  yet  in  general,  with  the  same  current 
it  was  found  to  be  less  than  1  per  cent  of  that  of  the  direct  current.  This 
feature  may  have  a  controlling  influence  in  the  adoption  of  alternating-cur- 
rent motors  for  city  work.  I  know  that  in  certain  European  cities  this 
matter  is  coming  forward  rapidly  and  certain  European  engineers  have 
told  us  that  they  will  be  obliged  to  adopt  alternating  current  on  their  rail- 
way lines  within  a  comparatively  short  time  on  account  of  difficulties  from 
electrolysis  with  their  direct- cur  rent  systems. 

It  has  been  mentioned  that  the  character  of  the  load  on  an  alternating- 
current  railway  system  is  different  from  that  of  the  direct-current  system. 
It  is  different  in  several  ways.  The  proportion  of  load  in  the  power-house 
will  differ  from  that  of  the  direct-current  system,  because  in  starting  and 
accelerating,  the  load  will  be  to  a  certain  extent  inductive,  which  repre- 
sents no  energy.  This  inductive  element,  while  not  representing  energy, 
does  represent  torque.  Therefore  in  starting  and  at  low-speeds  while 
accelerating,  a  considerable  proportion  of  the  current  supplied  to  the  car 
represents  no  energy  and,  therefore,  represents  no  energy  load  on  the  power 
station.  In  this  feature,  the  single-phase  system  resembles  the  present 
locomotive  system  in  taking  least  power  at  start,  with  the  amount  of 
power  increasing  as  the  speed  increases.  If  there  were  no  losses  in  the 
motor  itself  and  the  control  system,  then  the  car  would  start  with  zero 
energy,  and  the  energy  consumed  would  rise  proportional  to  the  power 
actually  consumed  in  accelerating  and  driving  the  car.  This  woul-d  be 
true  only  when  potential  control  is  used  and  all  rheostats  are  omitted. 

This  inductive  load  taken  by  the  motors  at  start  will  have  very  much 
the  same  effect  on  the  alternating- current  generators  as  if  an  energy  load 
were  carried,  but  represents  an  extremely  small  additional  power  required 
to  drive  the  generator.  This  load  also  has  an  effect  on  the  regulation  of 
the  generators.  But  experience  has  shown  that  this  regulation  can  be 
taken  care  of  very  readily  by  means  of  voltage  regulators  in  the  generat- 
ing plant.  Such  voltage  regulators  are  very  satisfactory  for  railway  service 
and  can  operate  sufficiently  rapidly  to  hold  an  average  constant  potential,, 
although  it  may  not  be  exactly  constant;  but  in  general  the  regulator  will 
maintain  as  good  regulation  at  the  generator  as  is  obtained  in  direct- 
current  railway  service  by  means  of  the  series  coils. 

On  the  question  of  polyphase  motors  for  Tailway  service,  it  has  foeea 
brought  out  repeatedly  before  the  American  Institute  of  Electrical  En- 
gineers, that  American  engineers  do  not  consider,  and  have  not  considered,, 
the  polyphase  motor  a  satisfactory  one  for  railway  service,  largely  on. 
account  of  the  characteristics  of  the  motor  itself,  and  also  on  account 
of  the  two  overhead  conductors.  A  European  engineer  told  me  some  time- 
ago  that  he  had  made  a  careful  investigation  of  the  question  of  poly- 
phase railways  in  Europe.  He  stated  that  in  some  of  the  railways  where- 
a  single  trolley  was  used  with  two  wheels  or  rollers,  the  question  of  keep- 
ing the  two  overhead  conductors  exactly  parallel  to  each  other  seemed! 
to  him  to  be  an  almost  insurmountable  difficulty,  and  that  while  it  was. 
being  done  in  a  number  of  instances,  he  did  not  consider  it  practical,  and! 
be  would  not  have  any  arrangement  that  required  as  much  careful  adr- 


212      STILLWELL:     WILKESBARRE  &  HAZELTON  RAILWAY. 

justment  as  is  required  in  these  cases.  This  man  was  a  mechanical  en- 
gineer rather  than  electrical,  and  his  criticisms  were  mostly  on  the 
mechanical  construction.  I  have  had  no  experience  myself  with  such  an  ar- 
rangement, but  it  seems  to  me  that  with  two  overhead  trolley  wires  it 
would  be  advisa-ble  to  have  two  trolley  poles  with  independent  movement. 
I  do  not  believe  that  the  polyphase  system  will  ever  come  into  extensive 
use  in  this  country,  as  the  characteristics  of  the  motors  themselves  will 
prohibit  it. 

In  connection  with  the  use  of  the  single-phase  alternating  current  on 
heavy  railway  service,  I  happen  to  know  that  in  the  case  of  some  of  the 
larger  railways  in  this  country,  many  of  the  engineers  are  fully  con- 
vinced that  they  will  be  obliged  to  transform  their  roads  to  the  electric 
system  in  a  very  few  years'  time,  and  many  of  them  believe  that  an  alter- 
nating system  will  be  adopted.  The  Pennsylvania  Railroad  Company 
adopted  direct  current  for  their  New  York  terminal,  but  a  number  of  their 
engineers  are  not  sure  whether  they  have  done  the  right  thing  in  adopting 
direct  current.  They  have  adopted  direct  current  for  very  much  the  same 
reason  as  given  by  Mr.  Sprague  in  the  case  of  the  New  York  Central,  viz., 
it  was  something  which  has  been  tried  and  proved  to  be'  operative.  Never- 
theless, a  number  of  these  engineers  feel  that  by  the  time  the  direct-cur- 
rent system  is  completely  installed  on  the  New  York  terminus,  they  will 
find  they  should  have  adopted  the  alternating  system.  But  they  are  irt  the 
same  position  as  a  number  of  the  street  railways  many  years  ago  in  regard 
to  the  use  of  the  cable  system  instead  of  the  electric  system;  in  some  in- 
stances the  cable  system  was  adopted,  as  it  was  known  to  be  an  operative 
one,  while  at  the  same  time  the  engineers  felt  that  the  cable  system  would 
have  to  be  taken  out  in  a  very  few  years'  time.  It  has  been  cited,  in  the 
adoption  of  direct  current  on  the  above-named  steam  roads,  that  as  it 
proved  an  advisable  method  to  install  the  cable  system,  even  with  the  ex- 
pectation of  throwing  it  out  later,  so  will  it  prove  to  be  advisable  to 
install  direct  current  on  the  railway  terminals  with  the  expectation  of 
changing  later  to  the  alternating.  As  stated  before,  many  of  the  engineers 
are  satisfied  they  will  throw  out  the  direct  current  before  many  years, 
and  they  recognize  that  a  fundamental  reason  for  making  the  change  will 
appear  when  they  begin  to  extend  their  system,  and  they  see,  before  the 
terminal  system  is  in  entire  operation,  that  the  advisability  for  extension 
must  be  considered. 

Mr.  E.  KILBTJRN  SCOTT  :  I  think  that  the  question  of  working  main 
lines  and  suburban  lines  we  will  have  to  settle  from  the  standpoint  of  the 
ordinary  mechanical  locomotive  engineer,  and  I  cannot  conceive  of  ten 
•of  those  men  being  brought  in  front  of  a  three-phase  motor  on  the  one 
hand  and  a  single-phase  motor  on  the  other,  with  a  commutator,  or  a 
direct  motor,  not  seeing  or  think  that  the  three-phase  motor  was  the  thing. 
That  kind  of  man  has  more  respect  for  the  three-phase  than  we  have. 
We  have  seen  it  grow  from  a  crude  apparatus  to  the  perfect  piece  of  work, 
but  it  seems  to  me  it  is  very  complicated,  and  I  cannot  conceive  for  a 
moment  of  the  ordinary  mechanical  engineers  considering  the  commutator 
1  machine.  The  thing  that  will  decide  them  in  England  will  be  absolute 
.simplicity  of  apparatus  and  safety  of  human  life,  and  on  the  question  of 


8TILLWELL:     WILKESBARRE  d  HAZ ELTON  RAILWAY.      213 

simplicity,  the  three-phase  motor  without  any  commutator  it  seems  to  me 
has  the  advantage. 

On  the  question  of  human  life,  while  we  have  got  the  three-wire  system, 
it  has  come  over  to  us  with  the  commutator  and  we  do  not  like  it.  We 
would  rather  have  less  efficiency  and  a  more  stable  machine.  Regarding 
the  third  rail,  we  have  it  as  I  say  —  what  we  call  experimenting  with  it. 
That  is  about  as  far  as  we  go,  because  I  am  sure  if  we  kill  off  very  many 
men  on  the  Northwestern  Road  there  will  be  such  an  outcry  in  the  papers 
that  we  will  have  to  give  it  up.  Because  we  consider  human  life.  In 
our  country,  we  do  not  have  what  I  see  here  and  which  it  amazes  me  to 
see,  we  do  not  have  railway  lines  running  along  streets  with  only  level 
crossings.  We  do  not  have  railway  trains  running  over  surface  tram- 
v/ay  lines.  We  do  not  have  that;  so  we  do  not  have  that  problem  regard- 
ing the  combination  of  single-phase  and  direct  currents. 

Now,  take  the  three-phase  motor  again.  I  raised  this  point  the  other 
day  and  it  was  not  answered.  In  a  single-phase  motor  surely  you  have  the 
current  going  to  maximum  and  back  to  zero  again  and  again  to  maximum. 
It  seems  to  me  if  you  had  to  take  a  fair  test,  say  a  locomotive  equipped 
with  the  three-phase  motor  and  one  equipped  with  the  single-phase  and 
commutator,  it  seems  to  me,  to  draw  a  certain  train  of  a  certain  weight, 
say  ten  tons,  you  would  require  a  heavier  locomotive  in  the  case  of  the 
single-phase  than  you  would  in  the  three-phase.  I  have  not  that  answer. 
Suppose  it  was  five  to  one,  the  usual  ratio,  that  is  to  say,  ten  would  re- 
quire a  fifty-ton  locomotive,  a  fifty-ton  three-phase  locomotive  draws  this. 
I  think  if  it  were  equipped  with  a  single-phase  commutator  it  would  have 
great  difficulty. 

Suppose  you  are  on  a  steep  grade,  the  brakes  are  down.  You  know  when 
you  start  your  steam  locomotive  you  release  your  brake.  Now,  suppose 
the  train  was  very  heavy  and  suppose  the  train  brakes  did  not  come  off, 
wouldn't  this  be  the  condition  of  the  single- phase  commutator  motor?  It 
would  be  standing  still  and  would  have  full  voltage  and  full  current  in 
the  motor,  the  armature  would  be  going  as  a  static  transformer,  and  the 
coils  underneath  the  brushes  being  on  short-circuit.  Wouldn't  you  get 
breakages  of  the  current  through  those  brushes? 

We  used  to  make  a  single-phase  commutator  motor,  and  we  struggled 
for  nearly  a  year,  but  threw  it  out,  because  —  we  used  to  make  it  go 
all  right,  and  then  some  person  would  tack  it  onto  a  very  heavy  machine 
that  wouldn't  start  and  try  to  get  a  short-circuit  through  those  coils 
underneath  those  brushes,  and  the  thing  would  burn  out.  And  we  couldn't 
go  on  like  this,  and  we  couldn't  make  a  single-phase  motor  that  would 
work,  and  don't  make  them  for  actual  work. 

In  regard  to  variation  of  speed,  we  hear  a  great  deal  about  variation  of 
speed  and  control  and  arrest  and  all  that.  Now,  if  I  want  a  machine,  a 
motor  to  drive  a  Hoe  printing  press,  where  I  want  the  machine  to  go  very, 
very  slowly,  to  get  the  thing  in  shape  to  start  I  go  to  Mr.  Leonard,  I 
buy  one  of  his  apparatus  and  I  have  a  thing  that  will  crawl,  and  under 
certain  conditions  run  to  speed.  But  we  do  not  want  a  train  to  go  slowly, 
and  we  are  compelled  to  rely  on  the  three-phase  motor  in  the  operation 
of  trains. 


214      STILLWELL:     WILKESBARRE  d  UAZELTON  RAILWAY. 

Now,  in  regard  to  copper,  this  of  course  is  a  difficulty.  We  have  the 
two  arms  as  against  the  single  wire,  but  if  you  take  a  high  tension  system 
like  the  Oerlikon,  it  uses  three  wires.  There  is  one  more  wire  in  that,  but 
isn't  that  a  very  condition  where  you  have  to  give  something  in  order  to 
obtain  results  ?  Isn't  this  the  case,  that  you  have  a  certain  amount  of  bare 
wire  overhead,  or  a  certain  amount  of  insulated  wire  underground?  Now 
then,  if  you  have  a  system  which  calls  for  more  wire  overhead,  certainly 
you  are  better  off.  You  have  much  less  wire  underground  and  it  is  the 
insulated  wire  that  runs  away  with  the  money. 

Then  looking  at  it  from  the  point  of  the  crossings,  and  that  sort  of 
thing.  I  know  that  you  claim  in  the  three-phase  there  is  danger  in  the 
wires  going  over;  but  I  think  on  nearly  all  of  these  surface  systems  we 
are  talking  about  there  are  ways  of  protecting  all  these  difficult  crossings. 
If  you  want  to  give  a  speed  of  eighty  or  ninety  miles  an  hour  you  cannot 
have  curves.  We  cannot  run  on  our  present  tracks  eighty  or  ninety  miles 
an  hour.  The  inclination  of  the  rails  on  some  curves  would  be  so  great 
that  if  a  train  stopped  on  that  particular  point  it  would  topple  over. 
We  shall  have  to  straighten  out  our  tracks  and  take  away  those  difficult 
crossings  before  we  can  run  that  speed.  Then  you  see  all  the  objections 
to  the  three-phase  disappear. 

Anyway,  there  is  this  point  in  favor  of  the  three-phase  as  against  the 
single:  That  is,  if  you  have  a  three-phase  and  one  of  them  breaks  down, 
you  have  a  reserve  in  the  system.  If  you  have  a  single-phase  and  it  breaks 
down  it  is  gone,  and  if  yon  have  another  single-phase  you  have  got  to 
switch  it  in  or  leave  it  in  all  the  time,  but  as  I  say,  if  you  have  a  three- 
phase  system  and  one  of  them  breaks  down,  the  other  two  carry  the  load. 

Regarding  loss  of  time  in  shifting,  owing  to  the  fact  that  you  are 
running  with  a  three-phase  motor  with  alternating  currents,  the  traffic 
superintendent  knows  that  that  train  is  going  to  go  along  that  track  at  a 
certain  speed.  It  may  have  a  greater  speed  going  up  an  incline,  but  the 
fact  he  knows  that  that  driver  must  run  across  the  track.  Being  driven 
by  a  three-phase  motor  is  an  advantage  I  think  in  traffic  work.  Suppose 
the  train  got  behind  time,  and  to  make  that  up  of  course  the  three-phase 
motor  can  make  over-speed,  and  the  traffic  people  I  have  spoken  to  about 
it  —  steam  locomotive  traffic  people  —  don't  see  much  trouble  there. 

At  any  rate,  in  this  matter  I  really  think  that  although  there  has  been 
a  great  deal  said  here  about  single-phase,  because  the  two  big  companies 
in  this  country  decide  on  single-phase,  it  does  not  settle  the  question. 
There  is  a  good  deal  to  be  said  on  the  other  side.  Dr.  Steinmetz  said 
that  our  three-phase  systems  in  Europe  were  on  a  level  not  far  from 
perfection,  and  every  company  has  received  permission,  or,  rather,  been 
asked  by  the  government,  to  extend  their  lines.  Do  you  think  the  Italian 
government  would  have  asked  the  Ganz  Company  to  extend  that  line  unless 
it  was  a  magnificent  success?  It  is  a  magnificent  success. 

Mr.  H.  WARD  LEONARD:  For  thirteen  years  I  have  urged,  and  I  wish 
to  urge  once  more,  an  electric  railway  system  having  the  features  which 
characterize  the  system  identified  with  my  name:  First,  single-phase 
high-tension  generation,  transmission,  and  conduction  by  moving  contact 
upon  the  train.  Second,  means  on  the  train  for  deriving  in  a  local,  sepa- 


ST1LLWELL:     WILKESBARRE  6  HAZELTON  RAILWAY.      215 

rate,  insulated  working  circuit  a  current  of  lower  voltage  which  is  sup- 
plied to  the  propelling  motors.  Third,  means  on  the  train  for  varying 
from  zero  to  the  maximum,  and  without  waste  energy,  the  working  electro- 
motive force  in  the  local  circuit.  I  think  I  am  safe  in  saying  that  nearly 
all  modern  single-phase  systems  have  these  essential  features. 

For  passenger  service,  and  for  light  freight  and  express  service,  the 
variable-speed  single-phase  alternating-current  motor  may  be  found  suffi- 
ciently satisfactory,  but  for  the  heaviest  freight  service  I  am  more  con- 
fident than  ever  before  that  it  will  be  necessary  to  transform  upon  the 
train  the  single-phase  energy  into  continuous-current,  variable-voltage 
energy  and  supply  it  to  direct-current  propelling  motors,  as  I  have  urged 
continuously  since  1891. 

As  a  large  number  of  engineers  who  are  attending  here  have  asked  me 
as  to  the  progress  that  I  am  making  with  this  system  of  mine,  I  will 
njention  somvi  points  in  connection  with  it.  I  first  publicly  described  this 
system  in  a  patent  in  1891,  and  I  read  a  paper  entitled  "  How  Shall  We 
Operate  an  Electric  Railway  Extending  100  Miles  from  the  Power  Sta- 
tion "  in  1894  before  the  American  Institute  of  Electrical  Engineers. 
The  first  recognition  of  the  system  came  from  Col.  Crompton,  who  in  his 
presidential  address  before  the  Institution  of  Electrical  Engineers  of  Great 
Britain,  in  1^5,  I  think,  predicted  that  it  had  features  which  would  give 
it  great  importance  in  electric  traction  work.  Mr.  Huber  of  the  Oerlikon 
Company,  in  1902,  and  Mr.  Mordey  of  Great  Britain  in  1902,  after  analyz- 
ing the  traction  problem  carefully,  concluded  that  this  system  was  the 
only  one  that  had  been  proposed  which  gave  commercial  promise.  The 
Oerlikon  Company  took  a  license  under  my  patents  in  1902,  and  proceeded 
to  construct  a  locomotive  which  since  then  has  been  tested. 

In  1902  the  celebrated  engineer  of  Sweden,  Dahlander,  as- the  head  of 
a  commission  appointed  by  the  Crown  to  investigate  the  question  whether 
electric  traction  could  supplant  steam  traction  on  3,000  miles  of  railway 
owned  by  the  government  of  Sweden,  after  giving  careful  consideration 
to  the  matter,  first  eliminated  the  continuous  current  for  transmission; 
and  second  eliminated  all  but  single-phase  alternating  current  for  trans- 
mission; and  finally,  after  considering  the  systems  that  had  been  pro- 
posed to  that  date,  reported  in  favor  of  my  system.  And  after  giving 
consideration  to  the  cost  of  installation  and  of  maintenance  and  of  de- 
preciation and  operation,  and  after  providing  a  sinking  fund  at  the  rate 
of  3  per  cent  per  annum  to  retire  the  bonds  which  would  be  issued  there- 
for, thus  retiring  the  first  cost  of  investment  in  thirty-three  years,  they 
concluded  that  my  system  would  show  a  saving  to  the  government  of 
Sweden  of  $2,000,000  per  annum  over  existing  methods  of  operation  by 
steam.  This  is  the  same  system,  I  may  say,  that  the  General  Electric 
Company  had  reported  upon  by  three  engineers  twelve  years  ago,  and 
each  of  the  three  engineers  condemned  the  system,  and  each  for  a  different 
reason. 

The  first  engineer  condemned  it  on  the  score  that  the  transmission  ana 
utilization  of  single-phase  alternating-current  energy  at  any  such  voltage 
as  I  proposed  —  which  was  from  10,000  to  20,000  volts  —  was  absurd  and 
beyond  consideration.  The  second  engineer  decided  that  I  evidently  had 


216     8TILLWELL:     WILKESBARRE  d  HAZELTON  RAILWAY. 

given  no  consideration  to  the  question  of  sparking,  and  that  it  was  utterly 
impossible  to  operate  a  system  such  as  I  proposed  on  account  of  the  dis- 
astrous sparking.  The  third  engineer  reported  that  I  evidently  intended 
to  use  some  very  complex  mechanism  in  restoration  of  energy  into  the 
line,  and  nothing  but  the  use  of  very  complex  mechanism  would  enable 
me  to  restore  the  energy  into  the*  line,  and,  therefore,  that  this  feature  was 
without  real  value. 

As  to  the  application  of  this  system  which  may  have  a  bearing  upon 
its  possibilities  for  railways,  I  may  say  it  has  been  operated  successfully 
in  a  number  of  instances  upon  elevators  since  1891  with  the  most  striking 
freedom  from  depreciation  and  a  most  striking  reliability  in  service,  and 
a  perfection  of  control  in  starting  and  making  a  landing,  which  is  so 
important  in  elevator  service. 

In  1893,  I  think  it  was,  the  Heilman  locomotives  made  use  of  this 
system  of  mine,  and  although  the  Heilman  locomotive^  on  account  of  its 
enormous  weight,  proved  a  failure,  it  demonstrated  that  a  locomotive  of 
that  size  could  be  operated,  and  was  operated,  with  perfectly  satisfactory 
results  as  regards  control  and  performance  of  the  commutator  for  the 
large  generator  necessary  for  such  a  large  locomotive. 

About  1893,  this  system  was  first  installed  upon  the  turrets  of  the 
United  States  Navy,  and  to-day  no  other  system  is  used  for  the  opera- 
tion of  turrets  in  our  navy.  Great  Britain  has  quite  recently  decided 
to  try  it;  it  has  been  recently  installed  upon  a  British  battle-ship  "The 
Terrible."  Those  turrets  are,  I  think,  quite  comparable  with  the  service 
which  is  to  be  expected  in  the  handling  of  heavy  freight  trains.  One  of 
these  turrets  weighs  600  tons.  It  has  to  be  accelerated,  controlled,  re- 
tarded and  reversed,  and  that  enormous  mass  is  a  thing  which  presents 
the  greatest  difficulty  in  handling,  and  the  system  has  given  perfect  satis- 
faction and  no  other  system  has  been  employed. 

The  moving  platform  at  the  Paris  Exposition  probably  represents  the 
largest  mass  which  has  ever  been  accelerated  and  handled  and  controlled, 
under  single  control,  by  electricity,  and  that  moving  platform  employed  my 
system  of  control.  It  weighed  about  3600  tons.  It  was  practically  equiva^ 
lent  to  a  freight  train  upon  a  level  track  with  a  very  great  number  of 
curves.  It  had  to  be  brought  to  full  stop  and  run  at  full  speed,  and  it 
was  accelerated  every  day.  Now,  in  the  case  of  that  moving  platform, 
there  was  a  clear  demonstration  of  the  fact  that  a  freight  train  with  my 
system,  not  only  from  theory,  but  from  actual  current  and  voltage  read- 
ings, would  be  and  could  be  in  practice  brought  from  rest  to  full  speed 
with  an  amount  of  energy  which  under  no  conditions  would  be  greater 
than  the  energy  required  at  full  speed.  The  watts  during  the  period  of 
acceleration  were  always  less  than  the  watts  at  full  speed.  I  repeatedly 
took  the  readings  at  the  installation  and  have  those  figures  for  anybody 
who  is  interested. 

Other  applications  that  have  been  made  since  then  are  automatic  pump- 
ing, to  maintain  certain  definite  pressure  —  the  rate  of  pumping  being  auto- 
matically governed  by  the  work  performed;  electric  automobiles,  in  which 
the  source  of  power  is  a  gasoline  engine  on  board  with  my  system  for  the 
transmission;  electric  trains  such  as  are  now  being  operated  at  England 


STILLWELL:     WILKESBARRE  d  HAZELTON  RAILWAY.      217 

in  which  my  system  is  employed  for  electric  transmission  from  a  gas  engine 
on  the  train;  and  one  of  the  finest,  if  not  perhaps  the  finest  building  in 
New  York  city,  the  Times  Building,  is  now  about  to  start  in  operation 
with  my  system  as  applied  to  high-speed  passenger  elevators. 

The  Oerlikon  locomotive,  which  was  tested  in  May,  1904,  this  present 
year,  of  course  represents  the  thing  which  is  most  pertinent.  In  that 
locomotive,  the  transmission  line  employs  single-phase  14,000  volts;  the 
entire  control  is  by  means  of  one  lever,  in  starting,  stopping,  reversing, 
braking,  etc.  That  locomotive  was  tested  in  the  presence  of  a  large  num- 
ber of  engineers,  and  a  great  many  engineers  from  this  country  received 
invitations  to  be  present  at  the  trial.  The  locomotive  was  tested  to  a 
point  —  and  I  don't  know  but  further,  but  I  do  know  it  was  tested  as 
far  as  this  —  that  the  current  in  the  secondary  circuit  was  double  the 
normal  current  of  the  rated  horse-power.  That  is,  that  amount  of  cur- 
rent was  available  without  any  difficulty  whatever  as  regards  commutation. 

In  this  connection,  I  wish  to  speak  of  the  weight  and  cost  of  the  motor 
generator  by  comparison  with  the  weight  and  cost  of  the  necessary  motor 
generator  for  the  sub-station.  I  wish  to  point  out  that  in  my  system  the 
motor  generator  has  to  provide  only  the  power  sufficient  for  the  movement 
of  the  train  upon  which  it  is  located.  It  is  not  necessary,  as  in  the  case 
of  sub-stations,  to  provide,  for  emergency  purposes,  several  times  as  much 
capacity  in  the  converter  as  the  average  service  would  require. 

Mr.  Sprague  incidentally  mentioned  in  discussing  another  paper,  the 
other  day,  the  probable  necessity  in  the  case  of  the  New  York  Central  of 
installing  storage  batteries  in  order  that  he  might  get  a  fairly  uniform 
load  upon  the  sub-stations,  as  there  was  a  probability  at  all  times  of  there 
being  four  trains  in  a  section  to  be  supplied  by  a  sub-station,  and  at  other 
times  no  train.  This  I  think  will  emphasize  clearly  the  importance  of 
having  the  energy  transformer  on  the  train,  where  it  can  be  all  the  time 
loaded  and  operated  at  a  good  load-factor,  and  where  the  first  cost  will 
not  have  to  be  several  times  as  much  as  that  required  by  the  average 
demand. 

The  well-known  difficulty  of  controlling  large  motors  by  opening  circuits 
carrying  the  energy  of  perhaps  1000  horse-power  is  going  to  increase  very 
rapidly  as  the  amount  of  the  power  increases.  There  is  some  difficulty  in 
opening  a  circuit  of  100  watts;  it  is  worse  at  1000  and  much  worse  at 
100,000,  and  it  becomes  more  and  more  difficult  as  you  go  up.  And  I  am  not 
surprised  to  notice  that  the  best  engineers  in  the  various  countries  are 
to-day  attempting  to  avoid  that  difficulty  and  secure  the  speed  control  by 
voltage  control  rather  than  by  opening  circuits  and  adjustments  of  circuits 
and  resistances. 

Another  point  that  is  of  great  importance  in  this  connection  is  the 
multiple  control  of  a  number  of  units;  and  here  again  we  meet  with 
great  difficulty  in  attempting  to  open  these  circuits.  We  also  meet  with 
great  difficulties  due  to  the  size  of  the  conductors  that  must  be  carried 
along  the  train  to  carry  a  working  current  to  the  motors  distributed 
through  a  long  train.  In  the  case  of  my  system  the  size  of  the  wires 
will  be  determined  by  the  current  which  the  field  only  has  to  carry. 


218      ST1LLWELL:     WILKESBARRE  d  HAZ ELTON  RAILWAY. 

There  will  be  three  wires  that  carry  only  field  current,  and  there  will 
be  no  automatic  switches  and  no  control  of  controllers. 

The  restoration  of  energy  is  a  matter  which  is  as  old,  almost,  as  the 
art,  in  discussions.  So  far  as  I  am  aware  my  system  is  the  only  one 
which  does  restore  energy  from  the  condition  of  full  speed  to  the  condi- 
tion of  rest.  And  I  wish  to  emphasize  the  point  that  of  course  it  be- 
comes necessary  that  we  have  an  energy  transformation  in  order  that 
we  can  take  advantage  of  the  energy  of  retardation,  while  it  is  falling 
from  maximum  to  minimum,  and  continue  to  transform  that  energy 
into  electric  energy  having  a  voltage  sufficiently  high  to  force  energy  into 
the  line.  A  point  of  the  greatest  importance  in  all  of  these  problems 
is  the  frequency.  In  order  to  make  a  commercial  single-phase  alternat- 
ing-current motor,  we  are  being  driven  step  by  step  to  lower  and  lower 
frequencies.  We  all  know  the  disadvantages  of  low  frequencies  for  light- 
ing purposes.  A  comprehensive  system  generating  a  form  of  energy 
which  can  be  used  for  all  classes  of  light  and  power  is  of  the  greatest 
importance. 

This  Oerlikon  locomotive  is  the  first  single-phase  locomotive  which  has 
been  designed  for  standard  railway  service,  and  the  condition  of  the 
matter  now  stands  in  this  way:  It  has  been  approved  by  the  government 
of  Switzerland,  which  has  tested  it,  and  authority  has  been  given  to  the 
Oerlikon  works  to  extend  this  system -to  the  first  section  of  the  line  which 
is  to  be  equipped. 

I  appreciate  fully  the  fact  that  a  combination  of  patents  and  policy 
is  always  likely  to  make  inertia  in  this  country,  and  the  General  Electric 
and  the  Westinghouse  companies,  so  far  as  concerns  patents  and  as  con- 
cerns electric  railway  policy,  are  practically  in  combination.  It  is  the 
greatest  difficulty  for  engineers  of  this  country  to  receive  any  considera- 
tion for  a  railway  system  which  is  going  to  affect  the  existing  policy 
as  regards  patents  and  business  methods.  And  that  is  the  reason,  which 
no  doubt  many  of  the  foreigners  are  very  much  surprised  to  note,  that 
my  system  is  considered  favorably  by  leading  engineers  of  Sweden,  Switzer- 
land, Great  Britain,  and  France,  and  yet  is  not  used  in  this  country. 
The  query  is  naturally  made,  if  this  system  has  any  merit,  why  isn't  it  used 
in  America?  I  think  you  have  the  answer  in  my  remarks  as  to  the  inertia 
of  a  combination  of  patents  and  policy  of  such  overwhelming  size  in 
any  one  country. 

Of  course,  this  is  again  an  explanation  of  why  the  General  Electric 
Company  and  the  Westinghouse  Company  are  so  desirous  of  securing  a 
motor,  notwithstanding  its  immense  disadvantages  as  to  control,  which 
has  the  one  advantage  that  they  can  go  to  their  former  customers  who 
have  bought  from  them  500,000  kilowatts  already  installed,  and  say  to 
them  that  their  past  assurances  as  to  the  permanency  of  the  investment 
they  have  made  can  be  realized.  I  can  imagine  that  it  would  be  rather 
embarrassing  for  a  salesman  to  meet  a  gentleman  whom  last  year  and  year 
before  they  had  assured  that  if  they  bought  the  three-phase  transmission 
and  rotary  with  sub-station  and  series-parallel  control  of  the  series 
motor,  that  it  was  unalterable  as  far  as  they  could  see,  absolutely  per- 
manent, and  as  good  an  investment  as  a  gold  dollar, —  to  have  to  go  to 


8TILLWELL:     WILKESBARRE  &  HAZELTON  RAILWAY.      219 

these  same  investors  two  years  later  and  say  that  system  is  all  absolutely 
wrong,  and  that  the  real  thing  is  the  single-phase  transmission,  trans- 
formation to  lower  voltage  in  a  local  circuit  on  the  car,  and  a  voltage 
speed  control  instead  of  the  series-parallel  control. 

Naturally  this  would  be  a  very  embarrassing  situation  from  a  com- 
mercial standpoint, —  and  they  don't  say  that. 

What  they  do  say  is  "  We  have  devised  a  system  which  will  enable  you 
to  operate  with  either  alternate  or  continuous  current  in  the  same  motor 
and  this  has  the  advantage  that  you  can  use  the  500,000  kilowatts  capacity 
that  you  have  already  paid  us  for." 

Now,  that,  of  course,  is  very  good  business  on  the  part  of  the  General 
Electric  and  Westinghouse,  and  I  am  not  criticising  them  in  any  way 
as  to  their  business  policy.  I  am  merely  indicating  that  the  existing 
patent  combination  naturally  interferes  with  the  development  and  use  of 
the  best  ideas.  I  need  hardly  say  that  had  Mr.  Huber  been  in  the  employ 
of  either  of  the  principal  companies  of  this  country,  my  system  would  not 
be  installed  now. 

As  to  some  remarks  made  by  Mr.  Sprague,  I  should  like  to  touch  on 
one  or  two  points.  Of  course,  I  need  hardly  say  I  believe  absolutely  in 
the  single-phase  transmission.  But  I  agree  with  Mr.  Sprague  that  forever 
the  direct-current  motor  will  be  superior  to  the  alternating,  and  I  represent 
both  of  these  ideas  in  combination.  Reliability,  which  he  has  emphasized, 
is,  I  agree  with  him,  of  the  utmost  importance;  and  in  that  connection 
I  wish  to  point  out  that  there  probably  is  nothing  electrically  operated 
in  the  world  in  which  reliability  is  of  such  great  importance  as  the  turrets 
on  the  battle-ships.  No  matter  what  the  system  might  have  in  other 
regards  in  the  way  of  advantages,  if  it  were  not  absolutely  reliable,  or  as 
nearly  so  as  such  things  can  be  expected  to  be,  it  would  have  no  chance 
whatever  of  being  used.  Reliability  is  the  first  factor  in  the  control  of 
those  turrets. 

Another  point  Mr.  Sprague  has  commented  on  is  one  that  I  agree  with 
him  is  of  great  importance,  and  that  is  the  protection  of  the  people  in 
the  train  again  the  possibilities  of  danger  from  the  high  voltage,  due  to 
any  kind  of  break-down  or  due  to  any  leakage  between  the  transmission 
circuit  and  the  train  circuit.  And  in  that  connection  I  wish  to  point 
out  that  the  high-tension  current  on  my  system  goes  into  the  motor  end  of 
a  motor-generator  which  is  an  entirely  separate  and  distinct  unit,  that  it 
is  electrically  and  mechanically  separate  and  insulated;  and  this  is  very 
different  from  a  case  in  which  the  high-tension  circuit  is  placed  in  as 
close  proximity  to  the  working  circuit  as  the  ordinary  insulation  of  a 
static  transformer  would  put  it. 

In  the  case  of  the  Oerlikon  Company  installation,  they  employed  a 
moving  contact  at  the  rail  in  addition  to  the  overhead  one,  with  the 
idea  of  insuring  complete  safety  at  that  point  in  case  any  difficulty  should 
arise  as  regards  contact  at  the  wheel,  but  the  necessity  of  that  may  be 
open  to  debate.  I  am  inclined  to  agree  with  Mr.  Lamme, —  that  the  higher 
the  voltage  the  more  certainty  there  will  be  that  the  contact  will  be  pre- 
served at  the  ground.  Therefore,  I  think  that  the  thing  that  needs  to  be 
protected  most  is  the  working  circuit  on  the  train,  and  that  we  ought  to 


220      STILLWELL:     WILKESBARRE  d  HAZELTON  RAILWAY. 

keep  that  as  separate  as  we  can  keep  it,  and  not  get  it  as  close  as  we 
can,  with  only  a  thin  layer  of  insulation  between  it  and  the  transmission 
circuit  of  high  pressure. 

On  one  point  I  am  quite  at  variance  in  my  opinion  with  Mr.  Sprague. 
He  said  he  did  not  think  the  Pennsylvania  Railway  would  during  the  life 
of  most  of  us  extend  electric  traction  on  its  line  beyond  the  New  York 
tunnel  plant.  In  that  I  cannot  agree  with  him.  I  have  nothing  more 
than  my  faith  in  the  future  of  electric  traction  systems  to  justify  my 
opinion  —  I  don't  know  any  Pennsylvania  Railway  engineer's  opinion 
on  the  subject.  I  am  merely  banking  on  electric  energy  and  electric 
engineering. 

Mr.  Lamme  has  emphazed  the  importance  of  low  voltage  in  the  motors, 
but  he  made  the  error  of  saying  that  we  could  not  have  direct-current 
motors  for  railway  traction  without  having  rather-  high-tension  in  the 
secondary  circuit.  Of  course,  in  my  system  while  securing  the  advantages 
of  high-tension  transmission  the  advantages  of  the  low  voltage  in  the 
motor  circuit  can  be  fully  realized. 

On  the  subject  of  electrolysis,  I  agree  with  Mr.  Lamme.  It  is  one  of 
great  importance  and  is  going  to  cut  a  great  figure  in  electric-railway  work 
in  the  future,  and  of  course  in  that  regard  my  system  has  the  advantages 
that  are  common  to  all  alternating  systems. 

Referring  to  what  Mr.  Scott  said  about  the  crawling  motor,  and  how  if 
he  wanted  the  motor  to  crawl  he  would  use  my  system,  but  if  he  wanted 
full  speed  in  addition  to  crawling  he  would  use  the  three-phase  motor. 
I  want  to  say  that  the  General  Electric  has  three-phase  currents  and 
motors  at  their  command  and  are  no  doubt  as  competent  to  handle  them 
as  are  engineers  abroad.  In  large  central  stations,  in  which  one  of  the 
most  important  points  is  to  have  a  coal  hoist  which  will  hoist  the  coal 
reliably  night  and  day,  th'ey  do  not  use  the  three-phase  current,  which 
could  be  used  for  such  purposes,  and  which  I  should  judge  from  Mr.  Scott's 
remarks  he  would  consider  eminently  suitable  and  superior  to  my  system; 
but,  on  the  contrary,  with  the  three-phase  currents  right  there,  they  do 
install  a  motor  generator  and  my  system  for  driving  the  hoist,  because  it 
does  give  superiority  of  control  and  reliability  in  service. 

CHAIRMAN  DUNCAN:  May  I  ask  that  discussions  be  limited  to  ten 
minutes,  please. 

Mr.  B.  J.  ARNOLD:  I  am  going  to  try  and  avoid  saying  anything  about 
my  own  system  this  morning  —  not  that  I  am  ashamed  of  it,  because  I  am 
very  proud  of  what  has  been  done  with  it  as  a  pioneer  in  single-phase 
work,  regardless  of  its  merits.  I  do  not  know  what  my  friend  Sprague 
said  before  I  came  in,  but  I  do  not  know  that  if  it  were  not  for  the  fact 
that  he  remains  young  so  long  in  appearance  I  would  say  that  his  ideas 
of  late  years  are  quite  what  we  might  attribute  to  a  gray-headed  man  — 
but  he  has  not  turned  gray  fast  enough  to  justify  it.  But  I  do  know 
that  the  atmosphere  he  has  been  in  the  last  two  or  three  years  has  put 
a  certain  conservatism  into  him  which  is  very  admirable,  but  we  can- 
not get  him  away  from  the  direct-current  system  quite  as  rapidly  as  I  had 
hoped.  However,  he  has  maintained  a  consistent  position  on  the  matter  and 


STILLWELL:     WILKESBARRE  d  HAZELTON  RAILWAY.     221 

presents  the  merits  of  the  single-phase  as  strongly  as  he  feels  they  can 
now  be  advocated. 

Mr.  Lamme's  point  on  the  low  voltage  question  I  can  see  nothing  in  be- 
cause I  do  not  see  but  that  we  are  getting  along  very  well  with  500  volts 
with  direct  motors,  even  600  or  700  volts,  and  I  have  seen  no  difficulty  in 
using  alternate-current  motors  working  at  as  high  pressures.  I  think 
his  position  must  be  due  to  the  fact  that  there  is  some  other  reason 
for  using  low  voltage,  due  probably  to  the  method  of  control  or  some- 
thing else  which  he  has  not  made  clear.  I  am  not  able  in  the  time  at  my 
disposal  to  bring  out  all  the  technical  points  involved,  but  I  cannot  seo 
anything  in  the  argument,  and  there  is  a  certain  disadvantage  to  it  with 
the  systems  that  are  in  use,  because  you -must  make  and  break  this  low 
voltage  current,  which  is  objectionable.  There  are  certain  elements  both 
ways:  You  can  make  and  break  too  high;  you  can  make  and  break  too  low 
voltage. 

I  am  going  to  call  on  Dr.  Steinmetz  to  bring  out  some  other  points 
after  I  get  through.  The  point  made  by  Mr.  Scott  about  the  fact  that  it 
is  a  real  advantage  to  the  train  despatcher  to  have  railroad  trains  that 
run  at  a  certain  rate  of  speed  and  cannot  run  any  faster,  I  think  that  is 
a  very  poor  railroad,  and  if  we  had  an  association  of  train  dispatchers 
here  I  think  they  could  answer  the  argument  much  better  than  I  can. 
It  seems  absurd  to  me  to  say  that  we  do  not  want  railroad  trains  to 
run  high  speeds,  when  we  do  want  it  because  there  are  necessities  for  it. 

Mr.  SCOTT:     You  misunderstood  me,  sir. 

Mr.  ARNOLD:     I  do  not  mean  to  misrepresent  you. 

Mr.  SCOTT:  I  said  a  certain  railroad  had  its  rolling  stock  equipped 
for  certain  speeds. 

Mr.  ARNOLD:  That  is  what  I  said,  and  I  do  not  misrepresent  you. 
I  understand  you  to  say  you  thought  it  desirable  to  have  a  constant  speed. 

Mr.  SCOTT:  If  there  were  people  that  wanted  their  rolling  stock  for 
certain  speed,  and  wanted  to  run  it  higher  of  course  they  would  not  — 

Mr.  ARNOLD:  In  my  judgment  that  is  impractical  railroading;  however, 
I  am  only  one  individual. 

I  am  a  great  believer  in  as  much  simplicity  as  you  can  yet,  in  spite 
of  the  fact  that  I  have  adopted  complicated  means  to  arrive  at  simplicity. 
But  the  system  which  will  win  is  the  most  simple  one  and  the  one  which 
costs  the  least  money.  And  no  matter  what  our  present  ideas  are  as  to  the 
merits  of  the  various  systems,  that  is  the  thing  that  .will  finally  decide 
the  question.  And,  therefore,  I  maintain  that  the  two  wires  overhead  and 
three-phase  system  are  impractical  for  railroad  work.  We  have  got  to 
have  a  single  conductor,  and  if  we  could  eliminate  the  conductor  entirely 
we  would  be  as  nearly  perfect  as  possible. 

The  other  point  is  we  have  got  to  have  pretty  high  voltage  on 
our  working  conductor  due  to  inductive  loss  in  the  rail.  I  have  experi- 
mented with  voltage  as  high  as  6000  on  the  working  conductor  —  and 
haven't  killed  any  one  yet,  and  hope  not  to.  It  has  been  tried  by  the 
parties  I  represent,  as  you  know,  as  high  as  15,000  volts,  and  I  think  it 
was  tried  in  Mr.  Leonard's  locomotive,  which  so  far  as  I  can  learn,  has 
worked  fairly  successfully,  and  it  seems  to  me  the  nearest  approach  to 


222     8TILLWELL:     WILKESBARRE  d  HAZELTON  RAILWAY. 

perfection  of  means  for  getting  the  energy  on  the  train.  Mr.  Chairman, 
1  am  going  to  stop.  I  think  I  have  used  up  my  ten  minutes. 

Mr.  HENRY  PIKLER:  Permit  me  to  say  a  few  words  concerning  this 
subject.  I  want  to  refer  particularly  to  Mr.  Steinmetz'  discussion.  Mr. 
Steinmetz  gave  us  a  very  clear  and  concise  description  of  the  charac- 
teristics of  the  different  alternating-current  motor  systems,  and  pointed 
out  the  advantages  of  one  motor  system  above  the  other  in  the  railroad 
service.  The  conclusions,  however,  which  Mr.  Steinmetz  has  arrived 
at.  I  do  not  quite  agree  with.  Mr.  Steinmetz  treated  the  polyphase  induc- 
tion motor  rather  step-motherly,  and  I  think  he  called  it  an  unsuccessful 
attempt.  From  this  statement  it  appears  that  Mr.  Steinmetz  does  not  want 
to  recognize  the  fact  that  such  railroad  systems  are  in  a  very  satisfactory 
condition  of  operation.  I  refer  especially  to  the  Valtellina  three-phase 
railroad,  designed  by  the  Ganz  Company  of  Budapest,  the  experiments 
of  the  Siemens  &  Halske  Company,  and  similar  work  of  the  Brown-Boveri 
Company.  Of  course,  nobody  will  think  of  using  polyphase  induction 
motors  for  street-car  service  where  stops  are  frequent.  That  disad- 
vantage of  the  polyphase  induction  motor,  that  its  torque  decreases  with 
the  square  of  the  proportional  decrease  of  the  impressed  e.m.f.,  dis- 
appears when  the  central  station  and  sub-stations  are  reasonably  designed 
and  equipped. 

As  to  the  variation  in  the  speed  for  such  railways,  I  think  two  variations 
—  that  is,  the  highest  speed  and  the  half  speed —  are  entirely  satisfactory. 
Half  speed  may  be  obtained  either  by  concatenated  operation  of  two 
motors  or  by  changing  the  number  of  poles  as  has  been  done  by  the  Brown- 
Boveri  Company. 

These,  however,  are  general  points  in  comparison  with  other  motor 
systems,  but  if  we  would  go  into  the  details  of  design,  performance  and 
manufacture  of  the  motors  and  the  whole  railroad  equipment  we  find 
BO  many  points  in  favor  of  the  polyphase  induction  motor  that  it  makes 
it  much  more  desirable  than  any  of  the  present  systems  for  that  purpose. 
The  polyphase  railway  system  of  Valtellina  Railway  in  Italy  was  so  satis- 
factory in  service  that  the  Italian  company  accepted  the  entire  equipment 
before  the  expiration  of  the  test  period.  Discussion  or  hasty  experiments 
will  not  prove  the  advantage  or  disadvantage  of  one  system  or  the  other, 
the  future  and  long  service  in  actual  operation  will  effect  the  natural  se- 
lection of  the  best  system. 

Mr.  A.  H.  ARMSTRONG  :  I  want  to  give  two  or  three  historical  facts  con- 
nected with  three-phase  motor  work  in  this  country.  The  General  Electric 
Company  has  had,  from  time  to  time,  a  large  number  of  problems  sub- 
mitted to  it  in  connection  with  railway  work  upon  which  they  were  sup- 
posed to  pass  their  best  judgment  in  regard  to  motive  power.  Some  of 
those  problems  were  so  extensive  arid  called  for  such  peculiar  treatment 
that  the  direct-current  motor  failed  to  serve  the  purpose  in  every  case 
and  some  form  of  alternate  motor  was  necessary.  Up  to  within  the  last 
year  or  two,  the  three-phase  induction  motor  was  the  only  type  that 
could  be  considered,  and  we  have  unsuccessfully  tried  tor  the  past  ten 
years  to  adapt  a  constant-speed  limited-output  three-phase  motor  to  rail* 
way  conditions. 


STILLWELL:     WILKESBARRE  d  HAZEL  TON  RAIL  WAY.     223 

The  chief  objection  to  its  use  has  been  its  constant  speed  characteristic, 
which  would  make  the  locomotive  or  car  attempt  to  go  up  a  ten  per  cent 
grade  at  the  same  speed  at  which  it  operated  on  a  level, —  the  restricted 
output  of  the  motors  themselves,  which,  together  with  their  poor  power- 
factor,  made  the  system  expensive  to  install  and  operate. 

Most  of  our  suburban  railways  have  a  very  irregular  profile,  ranging 
from  a  level  track  to  4  or  5  per  cent  grade,  and  in  such  cases  the  motive 
power  must  be  designed  to  haul  the  car  or  train  on  the  maximum  grade, 
and  still  operate  efficiently  on  level  track.  A  5  per  cent  grade  will  re- 
quire a  tractive  effort  of  110  Ibs.  per  ton  or  more,  while  a  level  track 
will  require  twenty  Ibs.  or  more;  thus  the  motor  may  be  called  upon  to  de- 
liver five  or  six  times  its  normal  torque  when  operating  on  maximum 
grade.  Furthermore,  the  torque  of  the  induction  motor  varies  as  the 
square  of  the  line  potential,  and  must  have  sufficient  margin  to  take 
care  of  the  fluctuations  in  trolley  potential  which  will  occur  in  a  com- 
mercial railway  system.  Giving  due  recognition  to  the  fact,  further,  that 
the  motor  and  distributing  system  all  operate  at  a  poor  power-factor,  it 
becomes  necessary  under  the  conditions  of  commercial  operation  to  design 
the  induction  motor  for  such  a  large  maximum  torque  that  it  will  operate 
normally  at  a  small  percentage  of  its  maximum  output,  with  consequent 
poor  constants. 

The  variable-speed  motor,  of  which  the  commutator  motor  is  the  best 
type,  is  especially  adapted  to  railway  work,  because  it  embodies  most  of 
the  characteristics  wherein  the  three-phase  motor  is  deficient.  It  is  a 
variable-speed  motor,  and  follows  the  footsteps  of  the  direct-current  motor, 
which  has  proved  itself  well  able  to  take  care  of  general  traction  prob- 
lems. Its  output  is  unlimited,  in  a  railway  sense;  that  is,  the  motor  can 
slip  its  wheels,  which  is  all  that  is  required;  and  its  general  speed  char- 
acteristics, being  of  a  variable-speed  nature,  are  well  adapted  to  the 
fundamental  requirements,  not  only  of  suburban,  but  also  of  main-line 
high-speed  railways. 

I  believe  that  the  company  which  I  represent  have  been  justified  in 
passing  over  the  three-phase  motor  as  not  being  adapted  to  general  rail- 
way conditions,  and  were  wise  in  waiting  until  a  motor  had  been  de- 
veloped which  embodied  more  of  the  good  characteristics  of  the  direct- 
current  series  motor. 

Mr.  B.  G.  LAMME:  I  wish  to  add  something  to  Mr.  Leonard's  remarks 
in  regard  to  the  Swedish  railway  problem.  Mr.  Dahlander,  the  Swedish 
engineer  mentioned  by  Mr.  Leonard,  made  a  report  to  the  Swedish  gov- 
ernment on  the  question  of  electrification  of  the  Swedish  railways,  and 
in  this  report,  if  my  memory  serves  me  right,  the  system  which  showed 
the  least  cost  was  the  Westinghouse  single- phase  system,  but  it  was  con- 
sidered to  new  and  untried  to  be  recommended.  That  was  about  two 
years  ago.  Since  that  time  Mr.  Dahlander  visited  this  country,  and 
among  other  places  he  visited  the  Westinghouse  works  at  East  Pittsburg 
and  saw  the  Westinghouse  system  in  operation.  He  evidently  reported 
favorably  on  his  return  to  Sweden,  for  since  that  time  an  electric 
locomotive  has  been  ordered  from  the  Westinghouse  Company  by  the 
Swedish  Government.  This  locomotive  is  to  be  equipped  with  single- 


224      STILLWELL:     WILKESBARRE  cC   HAZELTOX  RAILWAY. 

phase  motors  of  a  frequency  of  twenty-five  cycles  per  second,  with  a 
maximum  voltage  of  18,000  volts  on  the  trolley  line.  The  conditions  are  so 
arranged  that  different  voltages  can  be  tried  on  the  trolley,  with  the 
maximum  stated  above.  It  is,  therefore,  evident  that  all  of  the  European 
engineers  do  not  favor  the  motor-generator  locomotive  system,  as  this 
order  was  placed  after  an  investigation  of  all  various  systems  proposed 
by  the  different  companies.  It  may  be  noted  that  the  Swedish  Govern- 
ment has  also  placed  orders  with  certain  other  companies  for  trial  equip- 
ments, and  in  all  cases  these  equipments  comprise  single-phase  alternating- 
current  commutator-type  motors. 

It  has  been  suggested  by  Mr.  Arnold  that  we  did  not  adopt  low  voltage 
on  the  alternating-current  motors  in  order  to  avoid  danger  of  grounds, 
but  that  this  voltage  was  used  for  other  reasons.  It  was  not  my  inten- 
tion to  give  the  impression  that  the  voltages  of  200  to  250  were  chosen 
for  this  particular  reason,  but  such  voltages  being  fixed  by  features  of 
design,  there  were  compensating  advantages.  I  intended  to  bring  out  that 
the  motors  being  wound  for  250  volts  instead  of  500  volts,  our  insulation 
stresses  would  necessarily  be  less  than  on  the  direct  current. 

Another  point,  which  has  not  been  brought  out  to  any  great  extent,  is 
the  rail  loss  with  alternating  currents.  In  this  country  practically  all  rail 
work  is  being  done  at  twenty-five  cycles,  and  even  at  this  low  frequency, 
the  rail  loss  is  high.  In  some  cases  we  he  <?e  found  it  to  be  about  four 
times  as  great  as  with  corresponding  direct  current,  while  in  other  cases 
it  was  even  higher.  This  means,  of  course,  that  relatively  high  alternating- 
current  voltages  are  used  on  the  trolley,  or  the  alternating  current  should 
be  fed  into  the  track  at  more  frequent  intervals  if  high  voltage  is  not  used. 
Another  way  to  reduce  this  loss  will  be  by  the  adoption  of  lower  frequency 
such  as  fifteen  to  twenty  cycles  per  second,  as  is  done  on  some  of  the 
European  polyphase  roads.  This  may  be  an  important  factor  in  fixing 
the  frequency  when  it  comes  to  equipping  the  large  railroads  electrically. 

In  connection  with  the  European  polyphase  roads,  I  will  mention  that  I 
visited  a  number  of  these  some  time  ago,  and  the  ones  I  saw  were  operated 
successfully  in  the  sense  that  they  were  doing  what  they  were  planned 
to  do.  These  roads  did  not  possess  the  flexibility  of  operation  that  we 
are  accustomed  to  in  this  country,  and  I  was  forced  to  the  conclusion  at  the 
time  that  the  reason  they  were  considered  successful  was  because  there  were 
no  corresponding  direct-current  systems  in  the  immediate  neighborhood 
to  furnish  a  comparison. 

Mr.  E.  K.  SCOTT  :     Two-  companies  in  Italy  are  running  two  lines. 

Mr.  LAMME:     I  did  not  see  those  lines. 

Mr.  E.  K.  SCOTT  :  The  governments  are  preparing  the  statistics  and 
have  been  doing  so  within  the  last  year.  They  are  within  a  few  miles  of 
each  other. 

Mr.  LAMME:  I  did  not  see  the  Valtellina  line.  The  data  which  we  have 
prepared  on  the  polyphase  railway  system  in  this  country  indicate  that 
where  polyphase  motors  are  used  for  frequent  starting  and  acceleration, 
they  could  not  compare  favorably  with  the  direct- cur  rent  system,  even 
when  arranged  with  the  "  tandem  "  or  "  concatenated  "  control.  That  fact 
was  brought  out  I  believe  two  or  three  years  ago  in  a  number  of  papers 
before  the  American  Institute  of  Electrical  Engineers. 


STILLWELL:     WILKESBARRE  &  HAZELTON  RAILWAY.       225 

Similar  data  has  shown  that  the  single-phase  alternating-current  system 
\vith  frequent  starting  and  acceleration  is  superior  to  the  direct  current  in 
efficiency.  The  single-phase  system  is,  therefore,  superior  to  the  direct- 
current  system  under  the  very  conditions  where  the  direct  current  is  far 
superior  to  the  polyphase  system. 

Mr.  P.  M.  LINCOLN  :  This  matter  of  additional  losses  in  the  rails  due  to 
alternate  currents  has  been  cited  as  a  very  serious  objection  to  the  alter- 
nate-current system.  I  would  like  to  say,  however,  in  that  connection  I 
have  figured  over  a  good  many  different  cases  where  alternate  currents 
have  been  proposed,  and  compared  the  same  with  direct  current.  Under 
normal  conditions,  the  alternate  current  with  a  thousand-volt  trolley  in- 
variably gives  a  lesser  loss  in  the  rails  than  does  the  direct  current  at 
500  volts, —  due  first  to  the  considerably  decreased  current  that  the  rail 
carries  on  account  of  the  higher  trolley  voltage;  and,  second,  to  the  closer 
supplying  of  sub-stations  which  can  be  allowed  with  alternate  currents 
over  direct. 

A  MEMBER:     You  mean  energy  loss? 

Mr.  LINCOLN:  The  energy  loss  is  much  less  in  the  rail  in  the  alternate 
current  of  1000  volts  than  it  is  with  500  volts  with  the  direct  current. 

Dr.  STEINMETZ:  Gentlemen,  the  position  which  I  take  regarding  the 
polyphase  induction  motor  is  not  that  such  motors  are  not  operative  on 
railroads,  but  that  the  single-phase  commutator  motor  is  far  superior, 
and  the  existence  of  polyphase  railways  shows  that  where  you  cannot 
use  anything  else,  or  believe  you  have  nothing  else,  it  can  be  made  to 
work,  after  a  fashion.  It  is  not  that  we  have  not  tried  the  polyphase  in- 
duction railway  motor  in  this  country:  since  more  than  ten  years  we 
have  been  very  energetically  working  on  the  polyphase  induction  railway 
motor,  until  we  finally  dropped  it,  only  a  couple  of  years  ago,  as  hopelessly 
inferior  for  the  general  requirements  of  railroading,  to  the  rotary-converter 
system  with  direct-current  motors,  and  to  the  single-phase  commutator 
motor.  We  have  never  built  any  induction  motor  railroad,  though  we  have 
been  hunting  hard  for  a  chance  to  do  so,  and  were  willing  to  build  it  with- 
out profit,  but  our  engineers  have  really  never  been  able  to  honestly 
recommend  a  customer  to  install  induction  motors,  but  even  where  con- 
ditions looked  very  favorable,  closer  investigation  threw  the  balance  de- 
cidedly in  favor  of  the  rotary  converter  system  with  direct-current  motors. 

Now,  the  rotary  converter,  which  here  in  the  States  has  been  standard 
apparatus  for  ten  years,  is  familiar  to  everybody,  and  known  to  be  abso- 
lutely reliable,  was  practically  unknown  abroad  until  it  was  introduced 
from  here,  and  is  still  viewed  by  some  engineers  abroad  with  some 
suspicion.  Hence  the  necessity  abroad,  to  make  the  induction  motor  go 
on  railway  cars,  while  here  the  converter  permitted  direct-current  supply 
over  unlimited  distance,  and,  therefore,  the  question  was  not  whether  the 
induction  motor  can  be  used  on  railways,  but  whether  it  offers  any  ad- 
vantage over  the  direct-current  motor  and  converter  system,  and  this  ques- 
tion was  answered  decidedly  in  the  negative. 

The  polyphase  induction  motor  is  a  very  beautiful  apparatus  when  run 
at  constant  speed.     But  you  cannot  run  it  at  more  than  one  speed.     It 
is  possible  to  get  half  speed  by  concatenation,  and,  if  anybody,  I  should 
ELEC.  RYS. —  15. 


226      8TILLWELL:     WILKESBARRE  rf  HAZELTON  RAILWAY. 

be  prejudiced  in  favor  of  this  because  I  invented  this  method  here  in  the 
United  States.  Mr.  Gorges  simultaneously  invented  it  abroad.  Unfortu- 
nately, in  concatenation  the  first  motor  carries  the  exciting  current  of 
both  motors,  and  when  using  the  very  small  air-gaps  customary  in  induc- 
tion motors,  or  the  still  smaller  air-gaps  our  European  friends  use,  the 
constants  of  the  motor  chain  may  still,  if  not  good,  at  least  not  be  hope- 
lessly bad,  especially  at  low  frequency.  But  I  have  never  been  able  to  get 
a  practical  electric  railway  engineer  even  to  consider  such  small  air-gaps, 
and  with  the  very  smallest  air-gaps  mechanically  permissible  in  railway 
motors,  and  the  great  limitations  in  space,  especially  in  diameter,  of  rail- 
way motors,  the  constants  of  the  motors  in  concatenation  (or  cascade  con- 
nection) are  usually  hopelessly  bad,  so  much  so  that  two  motors  in  con- 
catenation may  consume  more  current  than  both  motors  consume  when 
giving  the  same  torque  in  parallel  connection.  That  cuts  out  this  ar- 
rangement from  further  consideration. 

The  induction  motor  is  well  suited  where  you  desire  to  go  at  a  constant 
speed  and  load.  This  may  be  the  case  with  a  very  high  speed  railway, 
where  the  torque  required  when  running  at  full  speed  is  of  the  magnitude 
of  the  starting  torque.  Then  the  question  may  be  taken  up  again,  but 
not  under  ordinary  railway  conditions. 

.  Three-phase  requires  two  wires,  which  is  a  nuisance  and  which  is  un- 
endurable in  a  large  railroad  yard  —  where  one  wire  or  live  rail  is  just  one 
too  many. 

I  desire  to  say  one  word  regarding  my  friend  Mr.  Leonard.  I  can 
fully  corroborate  his  statements  on  the  beautiful  control  of  speed  and 
power  given  by  his  system.  You  are  able  thereby  to  start  with  power- 
ful torque  to  run  at  any  desired  speed,  run  very  slowly  at  constant  speed, 
stop  exactly  where  you  desire  to  stop  —  in  short,  get  a  most  beautiful 
control.  And  that  is  the  reason  why  his  system  is  used  for  the  turrets 
of  battle-ships,  and  to  a  certain  extent  in  high-grade  elevators. 

But  that  is  not  the  problem  of  the  electric  railway.  What  we  want 
from  the  railway  motor  is  to  get  away  as  quickly  as  possible,  to  run 
efficiently  at  high  speed  and  at  half  speed.  It  is  not  necessary  to  run  at 
any  and  every  speed  continuously.  But  what  we  want  of  the  railway  motor  is 
to  be  as  simple  as  possible;  that  is,  to  do  the  work  with  the  least  possible 
apparatus. 

As  regards  efficiency  of  operation,  if  we  look  at  the  characteristics  of  the 
single-phase  commutator  motor,  we  will  find  that  the  whole  range,  from 
stand-still  to  full  speed,  is  about  one-quarter  to  one  sixteenth,  in  which, 
with  rheostatic  control,  a  resistance  is  used  in  the  motor  circuits,  the 
rest  is  running  on  the  motor  curve;  that  is,  at  the  highest  possible  effi- 
ciency, so  that  even  in  a  service  requiring  very  frequent  starting,  if  we 
investigate  the  amount  of  power  which  could  be  saved  by  motor-generator 
control,  it  is  so  insignificant  as  not  to  warrant  the  complication.  But 
from  three-fourths  to  fifteen-sixteenths  of  the  speed  range,  or  during  by 
far  the  greatest  part  of  the  time,  Mr.  Leonard's  method  must  be  decidedly 
inferior  in  efficiency,  due  to  the  constant  losses  in  the  motor-generator  set 
(even  if  a  very  high-speed  set),  which  a  direct  operation  of  the  motor 


STILLWELL:     WILKESBARRE  &  HAXELTON  RAILWAY.      227 

As  regards  the  statement  relating  to  the  conservatism  of  large  com- 
panies, I  do  not  think  I  need  to  discuss  that;  but  it  is  possible  that  a 
conference  of  impartial  expert  engineers  does  not  always  look  at  an  in- 
vention quite  as  favorably  as  does  the  inventor  himself. 

To  return  to  the  railway  induction  motor,  I  had  quite  a  considerable 
and  variegated  experience  with  it,  and  no  doubt  so  did  others.  The 
first  complete  car  equipment  with  two  three-phase  induction  motors  was 
in  operation  on  the  experimental  track  of  the  General  Electric  Company 
in  1894.  It  came  to  grief  by  our  experimenting  on  a  very  short  track 
which  was  used  also  by  freight  cars,  in  trying  to  show  the  powerful  torque 
obtained  by  the  motor  brake,  on  reversing  the  motors.  I  believe  my  friend 
Armstrong  was  at  the  controller.  Unfortunately  one  of  the  two  trolleys 
came  oiF,  and  the  motor  ran  single-phase,  without  our  knowing  it  (by 
the  way,  another  early  claim  for  single- phase  railway  operation),  and  a 
freight  car  happened  to  be  a  very  short  distance  in  front  of  our  motor  car  — 
and  you  know  what  happens  when  an  irresistible  force  meets  an  im- 
movable body.  Since  then  we  have  built  several  more  equipments,  but,  aa 
I  stated  before,  we  never  have  felt  justified  in  recommending  three-phase 
induction  motors  for  railways. 

Mr.  F.  J.  SPBAGUE  :  My  friend  Mr.  Arnold  —  for  whom  no  one  has  a 
higher  affection  than  myself  —  would  seemingly  put  me  in  the  position  of 
an  opponent  of  the  alternating-current  motor,  and  suggests  lack  of  virility 
for  having  enlisted  too  heatedly  in  the  ranks  of  conservatism.  As  to  this 
last,  I  am  reminded  that  he  has  agreed  with  me  on  all  the  salient  points  of 
the  New  York  Central  equipment,  and  that  we  have  a  very  harmonious 
board.  The  five  gentlemen  composing  it  have  fought  out  their  difficulties 
over  the  table,  and  come  to  a  common  conclusion,  on  which  I,  for  one,  am 
quite  willing  to  stand. 

So  far  as  high  potential  is  concerned,  I  am  fully  aware  of  all  the  eco- 
nomic facts  achieved  by  its  use,  and  I  have  been  advocating  it  a  good 
many  years,  starting  with  600  volts  in  1886.  There  is  no  one  who  has  less 
antagonism  than  I  to  the  development  to  perfection  of  the  single-phase 
alternating-current  motor,  or  any  other.  As  engineers  we  hope  to  see  it, 
and  there  are  no  men  who  will  more  completely  welcome  the  perfect 
result  after  the  diseases  of  the  machine  have  been  cured. 

As  to  virility,  it  is  possible  that  age,  gray  hairs  and  wrinkles  are 
coming  upon  me,  but  if  so  they  may  tell  of  a  good  deal  of  hard  work  in  the 
past  twenty  years,  but  I  am  still  quite  ready  to  assume  any  responsibility 
required  by  an  engineer  within  the  limits  of  technical  risk  and  pocket- 
book.  My  gorge  rose  a  hit  when  Mr.  Leonard  spoke  of  the  multiple-unit 
system.  For  a  long  time  I  have  been  trying  to  hammer  the  definition 
of  "  multiple  unit "  into  the  electrical  dictionary.  It  is  not,  as  Mr.  Leonard 
indicated,  and  as  some  of  my  other  friends  have  described  it,  simply  an 
assemblage  of  motors  on  different  cars  under  common  control.  That  is 
not  necessarily  a  multiple-unit  system  —  and  I  must  beg  to  be  allowed 
to  speak  authoritatively  as  to  that,  because,  ungrammatical  as  the  term 
is,  I  happened  to  be  the  one  to  coin  it,  and  to  use  it  for  a  specific  pur- 
pose. It  is  simply  intended  to  define  a  system  of  a  plural  control  of  a 


-28      STILLWELL:     WILKESBARRE  d  HAZELTOX  RAILWAY. 

plurality  of  controllers  by  which  a  number  of  units  can  be  assembled  into 
a  train,  each  unit  being  absolutely  complete  without  any  dependence  upon 
or  relation  to  any  other  except  so  far  as  relates  to  control  of  the  several 
main  controllers;  the  propelling  motors,  main  controllers  and  collectors 
arc  all  individual  to  the  car  on  which  they  are  situated.  When  the  units 
arc  put  together,  and  through  a  secondary  system  they  are  controlled 
and  operated  from  one  or  more  points,  then  and  there  only  do  we  have 
multiple-unit  control. 

The  distinction  between  the  systems  mentioned  by  Mr.  Leonard  and 
others  and  the  multiple-unit  system  is  that  there  are  no  heavy  currents 
passing  from  car  to  car  in  the  latter.  The  only  currents  passing,  except 
where  shoes  are  connected  together  for  the  purpose  of  preventing  sparking 
on  icy  and  sleety  rails,  are  control  currents,  and  these  are  of  magnitude 
too  small  to  consider.  Mr.  Lamme,  since  he  refers  to  current  transmis- 
sion, must  have  missed  my  point  when  I  said  that  the  continuous-current 
motor  was  a  better  one  than  the  alternate-current  motor.  I  said  that, 
considered  only  as  a  motor,  in  the  matter  of  weight,  efficiency,  reliability, 
ease  of  construction,  and  reduction  of  liability  to  damage  when  working 
in  the  ordinary  way,  the  continuous-current  motor  is  the  superior.  The 
fact  is  the  present  effort  is  to  make  a  series  motor  run  on  alternating- 
current  circuits,  and  to  utilize  all  the  existing  advantages,  while  getting 
rid  of  some  inherent  difficulties  which  crop  up. 

Again  Mr.  Lamme,  or  some  one,  took  exception  to  the  question  of  danger 
that  might  arise.  I  do  not  care  to  what  potential  you  go,  there  is  a  period, 
fifty  times  a  second,  where  you  pass  zero.  If  at  that  time  the  car  is  on  a 
bad  rail  and  making  poor  contact,  and  there  is  a  leak  on  the  high-tension 
connection,  it  may  be  possible  for  a  person  boarding  the  car  from  moist 
earth  to  get  a  severe  shock. 

To  break  through  and  make  contact  from  wheel  to  rail  there  must  cer- 
tainly be  a  rise  of  tension  from  zero  to  some  point  which  is  necessarily 
sometimes  higher  than  might  exist  with  a  rail  arc  when  using  con- 
tinuous current.  I  do  not  wish  to  speak  as  an  alarmist,  or  say  that  these 
difficulties  will  not  be  overcome,  but  it  is  folly  to  ignore  them,  and  we  must 
recognize  the  defects  of  any  system  which  is  being  considered.  My 
criticism  is  we  are  apt  to  brush  aside  what  has  been  done  in  the  past,  and 
promise  too  much  for  a  new  departure,  because  it  fulfills  certain  con- 
ditions, and  that  we  ought  not  to  do. 

Dr.  STEINMETZ:  What  especially  impresses  me  is  that  induction-motor 
railways  have  been  run  seven  or  eight  years  ago;  the  commutator  motor 
has  been  brought  out  only  within  the  very  last  year  or  two.  But  the 
amount  of  interest  which  the  alternating  commutator  motor  has  raised, 
the  great  activity  displayed  in  all  countries,  compared  with  the  very 
low  activity  in  the  induction  motor,  give  me  the  general  impression  that 
the  commutator  motor  appeals  to  the  railway  engineers  as  greatly 
superior. 

CHAIRMAN  DUNCAN  :  Our  time  is  exhausted,  and  as  Mr.  Arnold  started 
the  discussion  I  will  ask  him  to  close  it. 


STILLWELL:     WILKESBARRE  d  HAZELTON  RAILWAY.      -29 

Mr.  ARNOLD:  I  think  it  is  pretty  thoroughly  closed  now.  We  hare 
pretty  well  covered  the  theory.  I  am  glad  to  see  the  sentiment  in  favor 
of  the  single-phase  motor,  regardless  of  what  it  has  done  in  the  past.  I 
am  bending  my  energies  to  it,  and  I  think  with  what  we  may  all  do,  we 
will  have  great  results  to  report. 


TRANSMISSION  AND  DISTRIBUTING  PROB- 
LEMS PECULIAR  TO  THE  SINGLE-PHASE 
RAILWAY. 

BY   PAUL  M.  LINCOLN. 


Up  to  the  present  time  practically  all  long  distance  power  trans- 
mission has  been  carried  on  with  three-phase  currents  on  account 
of  the  obvious  advantages  due  to  its  use.  The  use  of  single-phase 
currents,  however,  introduces  practically  no  new  elements  into  the 
transmission  problem.  Its  effect  is  to  simplify  the  arrangements 
both  of  the  line  and  the  translating  apparatus  at  the  ends  of  the 
line.  On  the  line  two  conductors  instead  of  three  will  be  used  with 
a  corresponding  reduction  in  the  number  of  insulators.  At  the 
terminals  one  transformer  will  take  the  place  of  a  group  of  three 
and  the  switching  apparatus  is  very  greatly  simplified. 

One  apparent  handicap  under  which  the  single-phase  line  labors 
is-  the  apparent  fact  that  to  transmit  a  given  amount  of  power  a 
given  distance  with  a  given  loss  requires  more  copper  single-phase 
than  three-phase  in  the  ratio  of  4  to  3.  If  we  assume  that  the 
voltage  between  the  single-phase  terminals  is  equal  to  that  between 
any  two  of  the  three-phase  terminals,  this  apparent  fact  holds. 
Under  normal  conditions  of  operation,  however,  this  assumption 
is  not  fair  to  the  single-phase  line.  It  is  evident  that  so  far  as 
the  transmission  line  is  concerned,  the  true  criterion  of  voltage 
strain  is  that  which  exists  between  any  conductor  and  ground  and 
not  the  voltage  between  conductors.  It  is  further  evident  that 
under  normal  conditions  ground  potential  will  exist  at  the 
geometric  center  of  the  electric  system.  For  instance,  ground 
potential  for  the  single-phase  line  will  exist  at  a  point  midway 
between  the  terminals  as  shown  at  (a)  Fig.  1,  while  in  the  three- 
phase  system  it  will  exist  at  the  geometric  center  of  the  triangle  as 
shown  at  (I}.  With  the  same  terminal  voltage,  therefore,  the 
insulation  strain  between  any  terminal  and  ground  will  be  the 
greater  in  the  three-phase  system  in  the  ratio  of  2  to  V3.  But  if 
the  terminal  voltage  be  so  adjusted  that  the  insulation  strains  to 

[230] 


LINCOLN  •     SINGLE-PHASE  RAILWAY  TRANSMISSION.       231 

ground  be  made  the  same,  then  to  transmit  a  given  amount  of 
power  a  given  distance  at  a  given  loss  will  require  for  the  single- 
phase  line  an  amount  of  copper  no  greater  than  that  required  by 
the  three-phase  line.  In  other  words,  for  equal  insulation  strains 
on  the  line  the  terminal  voltage  of  the  single-phase  system  may  be 
greater  than  that  of  the  three-phase  system  in  the  ratio  of  2 
to  V3. 

It  may  be  well  to  draw  attention  to  the  fact  that  the  above  ob- 
servation holds  good  only  for  the  normal  condition,  that  is,  the 
condition  that  ground  potential  occurs  at  the  geometrical  center 
of  the  system.  If  one  of  the  conductors  becomes  grounded  an 
abnormal  condition  arises  and  the  insulation  strain  becomes  equal 


FIG.  1. 

to  the  terminal  voltage.  Under  this  condition,  however,  the  three- 
phase  system  suffers  the  disadvantage  of  having  the  insulation  on 
two  conductors  subjected  to  a  strain  equal  to  terminal  voltage, 
while  in  the  single-phase  system  only  one  conductor  is  so  subjected. 
On  account  of  the  fact  that  a  polyphase  generator  is  for  a 
given  output  much  lighter  and  cheaper  than  a  single-phase  gen- 
erator, it  becomes  of  advantage,  so  far  as  the  generating  plant  is 
concerned,  to  derive  the  single-phase  currents  necessary  for  operat- 
ing a  single-phase  railway  from  polyphase  generators.  The  saving 
in  cost  of  generators  thus  effected  amounts  to  approximately  30 
per  cent.  In  order  to  secure  this  advantage  it  is  necessary  to  use 
a  switchboard  and  transformer  equipment  which  is  somewhat  more 
complicated  and  expensive  than  would  be  the  case  with  single- 
phase  generators,  but  as  a  rule  not  sufficiently  so  to  prevent  a 
greater  economy  in  the  use  of  polyphase  generators  over  single- 
phase.  For  this  purpose  the  two-phase  generator  is  in  general 
preferable  to  the  three-phase  since  it  is  easier  generally  speaking 
to  divide  a  given  amount  of  single-phase  load  into  two  parts  than 


232       LINCOLN:     SINGLE-PHASE  RAILWAY  TRANSMISSION. 

into  three  parts.  Three-phase  generators  can,  of  course,  be  used 
but  a  balanced  condition  of  load  is  obviously  more  difficult  to 
secure. 

The  use  of  single-phase  current  from  two  wires  of  a  three-phase 
line  also  involves  a  tendency  to  produce  disturbances  in  neighbor- 
ing telephone  and  other  circuits,  which  is  not  apparent  at  first 
thought.  Under  the  normal  condition  of  operation  of  a  three- 
phase  circuit  the  sum  of  the  static  potentials  of  the  three  phases 
i»  always  zero  at  any  and  every  instant  of  time.  Therefore,  static 
induction  on  neighboring  wires  is  due  only  to  the  fact  that  different 
distances  necessarily  exist  between  the  disturbed  circuit  and  each 
conductor  of  the  three-phase  circuit,  and,  therefore,  is  matter  which 
can  be  corrected  by  proper  transpositions.  If,  however,  one  of  the 
three  wires  be  taken  away,  as  may  be  the  case  with  a  single-phase 
from  a  three-phase  circuit,  the  sum  of  the  static  potentials  no 
longer  remains  at  zero  and  static  induction  will  take  place  on 
neighboring  circuits  without  the  possibility  of  correction  by  any 
method  of  transposition. 

In  other  words,  two  conductors  of  a  three-phase  circuit  will  under 
neighboring  circuits  equal  to  about  one-half  that  which  would  be 
occasioned  by  the  three  conductors  under  the  abnormal  condition 
arising  when  one  of  them  becomes  grounded.  Therefore,  if  there 
is  any  danger  of  disturbing  neighboring  circuits  by  static  induction, 
it  is  advisable  on  this  account  to  use  three  distinct  two-conductor 
circuits  rather  than  the  alternative  of  taking  single-phase  from  the 
three  conductors  of  a  three-phase  circuit.  An  alternative  is  to 
carry  all  three  of  the  conductors  to  all  points  to  be  served.  This 
often  involves  running  three  wires  where  two  would  carry  the  load 
simply  for  the  purpose  of  obtaining  the  static  influence  due  to 
this  third  wire.  Since  the  static  influence  is  independent  of  the 
material  of  the  wire  and  also  largely  independent  of  the  size  of 
the  wire,  this  third  conductor  need  not  necessarily  be  as  expensive 
in  first  cost  as  the  other  two  constituting  the  working  circuit. 

In  general,  therefore,  the  transmission  problem  is  changed  but 
little  by  the  adoption  of  single-phase  in  the  place  of  three-phase. 
But  when  we  come  to  the  problem  of  the  distribution  of  alternating 
current  to  cars  on  trains  along  the  line  of  a  railway  we  find  a 
material  difference  between  this  and  its  counterpart,  the  dis- 
tribution of  direct  current  to  railways.  In  the  following  discussion 


LINCOLN:     SINGLE-PHASE  RAILWAY  TRANSMISSION.       233 

it  is  assumed  that  the  general  arrangement  of  the  typical  alternat- 
ing-current railway  will  be  practically  the  same  that  is  now  fol- 
lowed in  the  typical  direct-current  railway.  That  is,  the  system 
will  consist  of  a  generating  station  sending  out  the  required  energy 
at  a  high  voltage.  At  various  points  along  the  line  this  high- 
voltage  energy  will  be  transformed  down  to  the  voltage  that  has 
been  selected  as  the  trolley  voltage  and  fed  directly  into  the  trolley. 
The  general  arrangement  of  the  alternating  and  direct-current  sys- 
tems is,  therefore,  very  similar.  The  main  differences  between 
the  two  systems  are,  first,  the  elimination  of  a  trolley  voltage  limit 
except  that  set  by  considerations  of  insulation  and  safety;  and 
second,  the  elimination  of  rotary  converters  from  the  sub-stations 
and  the  consequent  elimination  for  the  necessity  of  constant  at- 
tendance. 

Assuming  that  in  any  given  case  the  trolley  voltage  is  fixed, 
there  will  still  remain  two  variables  to  be  determined,  first,  the 
cross-section  of  the  trolley  copper,  and  second,  the  distance  between 
transforming  stations.  These  two  quantities  are  evidently  inter- 
dependent. That  is,  a  variation  in  one  requires,  in  order  to  render 
a  given  service,  a  variation  in  the  other.  For  instance,  if  we  in- 
crease the  number  of  feeding  points  the  cross-section  of  copper  to 
convey  a  given  amount  of  power  with  a  given  loss  is  decreased. 

The  considerations  upon  which  these  quantities  should  be  de- 
termined may  evidently  be  classed  under  the  following  heads: 

1.  Maximum  economy. 

2.  Voltage  drop. 

3.  Insurance  against  accident. 

4.  Mechanical  considerations. 

5.  Avoidance  of  undue  multiplicity  of  stations. 

1.  MAXIMUM  ECONOMY. 

It  is  evident  that  a  cross-section  of  copper  and  a  distance 
between  transforming  stations  should  be  used  which  will  give  the 
maximum  economy,  provided  the  limit  as  thus  set  does  not  fall 
beyond  that  as  absolutely  fixed  by  other  considerations.  Kelvin's 
law  gives  us  a  basis  for  the  calculation  of  the  most  economical 
cross-section  of  copper.  As  is  well  known,  this  cross-section  is 
dependent  only  on  the  cost  of  power,  the  cost  of  conductors  in 
place,  the  load  factor  and  the  interest  and  depreciation  on  the  in- 
vestment for  conductors.  Knowing  the  above  factors,  we  may 


234       LINCOLN:     SINGLE-PHASE  RAILWAY  TRANSMISSION. 

derive  at  once  the  density  of  current  per  unit  of  cross-section  of 
copper  which  will  be  most  economical.  This  current  density  per 
unit  of  cross-section  is  entirely  independent  of  the  distance  power 
i.-3  to  be  transmitted  as  well  as  the  amount  of  power  and  the  trans- 
mitting voltage.  Once  having  derived  the  most  economical  density 
of  current  per  sq.  in.,  it  is  easy  by  making  certain  other 
assumptions  to  fix  the  most  economical  distance  between  trans- 
forming stations  as  well  as  the  proper  size  of  copper.  The  most 
economical  distance  between  stations  is  given  by  the  following 
formula  : 


in  which 

D  =  distance  between  adjacent  transforming  station  in  miles. 

K  =  the  cost  of  a  single  transforming  station  in  dollars. 

V  =  trolley  voltage. 

A  =  most  economical  current  density  in  amperes  per  sq.  in.  as 
derived  from  the  conditions  mentioned  above. 

W  =  average  apparent  kilowatts  used  per  mile  of  road. 

P  =  price  of  copper  in  cents  per  pound. 

This  formula  is  simply  another  method  of  saying  that  to  make 
first  cost  a  minimum  the  cost  of  the  transforming  stations  should 
be  made  equal  to  the  cost  of  the  trolley  copper.  Knowing  the 
values  of  Af  D  and  W  the  cross-section  (in  circular  mils)  of  the 
trolley  is,  of  course,  fixed  by  the  expression 

6.35  X  1<»8  D  W. 
~VA~ 

To  derive  the  above  expression  for  distance  between  stations  the 
assumption  is  made  that  the  cost  of  a  transforming  station  is 
independent  of  its  capacity,  an  assumption  which  of  course  is  not 
strictly  true,  but  one  which  is  not  so  far  from  the  truth  as  appears 
at  first  sight.  The  total  cost  of  a  transforming  station  is  made 
up  of  transformers,  auxiliary  apparatus  and  building.  The  cost  of 
the  building  and  the  auxiliary  apparatus  will  remain  practically 
stationary  for  large  variations  of  capacity.  The  cost  of  the  trans- 
former item,  of  course,  decreases  with  decreased  capacity,  but 
decrement  in  cost  is  not  nearly  so  great  as  the  decrement  in 
capacity.  Further,  the  decrement  in  capacity  to  render  a  given 


LINCOLN:     SINGLE-PHASE  RAILWAY  TRANSMISSION.       235 

service  will  be  less  than  the  decrement  in  distance  between  stations. 
For  when  a  car  or  train  is  opposite  a  given  transformer  station 
practically  all  of  the  energy  to  operate  it  must  come  from  that 
transformer  station.  Within  wide  limits  too  the  maximum  load 
on  any  transformer  station  will  be  that  due  to  a  single  car  or  train. 
The  maximum  load  on  any  transformer  station  is,  therefore,  within 
wide  limits,  independent  of  its  spacing,  and,  therefore,  independent 
of  its  capacity.  Closer  spacing  only  limits  the  element  time 
during  which  the  load  pulls  on  a  transformer  station,  and  not  the 
element  of  maximum  load.  Since  the  capacity  of  a  transformer 
station  should  be  adjusted  to  the  root  mean  square  load  and  not 
to  the  average  load,  it  follows  as  stated  above  that  the  decrement 
of  capacity  in  transformer  stations  is  not  proportional  to  the  decre- 
ment of  spacing. 

As  indicated  above,  however,  the  consideration  of  economy  should 
be  allowed  to  fix  these  quantities  only  when  they  fall  within  the 
limits  as  fixed  by  other  considerations. 

2.  VOLTAGE  DROP. 

It  is  of  course  essential  that  sufficient  voltage  exists  at  the  car 
to  operate  it  and  it  is  preferable  that  the  fluctuation  of  voltage  be 
within  the  limit  of  successful  incandescent  lighting;  and  in  the 
spacing  of  transformer  stations  and  the  choice  of  trolley  wire  the 
dictation  of  economy  may  have  to  be  modified  by  the  dictation  of 
allowable  drop.  In  comparing  the  question  of  voltage  drops  in  an 
alternating-current  railway  line  with  those  of  a  direct-current  rail- 
way line,  two  marked  differences  obtain,  one  an  advantage  to  the 
alternating  system  of  distribution  and  one  a  disadvantage.  An 
advantage  for  the  alternating  system  accrues  from  the  general  fact 
that  alternating  voltages  are  capable  of  being  transformed  with 
comparative  ease  and  high  efficiency.  It  is  possible,  therefore,  to 
install  an  apparatus  on  an  alternating-current  car  whereby  any 
voltage  drop  that  occurs  may  be  compensated  for. 

On  the  other  hand,  the  alternating  system  labors  under  the  dis- 
advantage that  inductive  drops  which  are  peculiar  to  the  alter- 
nating system  are  added  to  the  ohmic  drop  which  is  the  only 
element  to  be  considered  in  the  direct-current  system.  The  amount 
by  which  the  total  drop  is  increased  by  this  inductive  effect  is 
dependent  of  course  upon  the  size  of  trolley  wire,  its  distance  from 
its  return,  the  nature  of  the  return,  the  frequency  and  the  power 


236      LINCOLN:     SINGLE-PHASE  RAILWAY  TRANSMISSION. 

factor  of  the  load.  The  general  statement  may  be  made,  however, 
that  with  25  cycles,  the  usual  height  of  trolley  wire,  the  usual 
power  factors  that  will  be  met  in  practice  and  sizes  of  trolley  wire 
not  exceeding  No.  4 —  the  total  drop  in  the  trolley  line  will 
rarely  be  more  than  the  ohinic  drop  increased  by  50  per  cent. 
This  figure  assumes  that  the  term  "  ohmic  drop  "  takes  into  con- 
si  deration  the  additional  loss  that  alternating  current  causes  in  the 
return  rail  circuit  over  that  caused  by  direct  current. 

3.  INSURANCE. 

A  second  point  which  should  be  borne  in  mind  when  determining 
the  size  of  trolley  and  the  distance  between  stations,  and  which 
may  require  a  modification  of  these  quantities  as  fixed  by  con- 
sideration of  economy,  is  the  possibility  of  the  temporary  break- 
down of  any  transformer  station.  These  elements  should  be  so 
chosen  that  in  this  event  operation  of  cars  or  trains  past  the  dis- 
abled station  may  be  effected  from  adjacent  stations.  This  con- 
dition may  fairly  be  considered  as  an  abnormal  one,  however,  and 
BO  long  as  operation  under  this  condition  still  remains  possible 
the  questions  of  economy  and  drop  may  be  lost  sight  of  in  that 
section  where  the  abnormal  condition  exists.  An  arrangement  of 
transformer  stations  which  may  be  suggested  in  this  connection  is 
one  in  which  a  reasonable  amount  of  spare  capacity  is  provided  by 
making  each  transformer  station  a  certain  percentage  larger  than 
necessary  to  take  care  of  its  normal  load,  and  only  providing  a 
single  transformer  in  a  station.  In  case  of  the  disablement  of  any 
station,  its  load  can  be  taken  care  of  by  the  adjacent  stations  until 
such  time  as  the  transformer  can  be  replaced. 

4.  MECHANICAL  CONSIDERATIONS. 

This  point  is  sufficiently  covered  by  the  consideration  that  the 
trolley  wire  must  be  on  the  one  hand  of  sufficient  size  to  make  a 
strong  mechanical  structure,  and  on  the  other  hand  not  of  so  large 
a  cross-section  as  to  make  the  supporting  structure  unduly  heavy. 
The  size  dictated  by  maximum  economy  must,  therefore,  be  subject 
to  the  modification  of  mechanical  fitness. 

5.  DANGER  OF  MULTIPLICITY  OF  STATIONS. 

In  viewing  this  problem  from  the  standpoint  of  the  high-tension 
line  it  must  be  borne  in  mind  that  every  point  at  which  it  is  neces- 


LINCOLN:     SINGLE-PHASE  RAILWAY  TRANSMISSION.       237 

sary  to  tap  the  line  and  take  power  becomes  a  point  of  danger,  a 
point  where  accidents  may  happen.  And  the  higher  the  high- 
tension  voltage  the  more  difficult  and  expensive  it  becomes  to  take 
power  from  the  line,  and  the  greater  becomes  the  liability  of  danger. 
This  point  becomes  a  good  reason  for  reducing  the  number  of 
transformer  stations  to  a  minimum. 

It  may  be  easily  gathered  from  the  above  discussion  that  there 
is  no  golden  rule  for  the  determination  of  the  spacing  and  capacity 
of  transformer  stations  or  the  size  of  the  conductor.  It  is,  like 
most  other  engineering  problems,  a  matter  of  compromise  between 
various  elements,  some  of  which  point  in  one  direction  and  some 
in  the  other,  and  a  matter  which  must  be  determined  by  engineering 
judgment  rather  than  by  any  inflexible  law. 


PROTECTION  AND  CONTROL  OF  LARGE  HIGH 
TENSION  ALTERNATING-CURRENT  DISTRIBU- 
TION SYSTEMS. 

BY  GEORGE  N.  EASTMAN,  Delegate  National  Electric  Light  Association. 


The  principal  object  to  be  attained  in  the  installation  of  pro- 
tective apparatus  is  continuity  of  service.  While  the  precautions 
that  are  necessary  to  be  taken  in  the  operation  of  one  system  may 
differ  materially  from  that  of  another,  the  protective  apparatus 
installed  to  insure  continuity  of  service  would  be  substantially  the 
same  for  either  system.  There  is  a  wide  difference  of  operating 
conditions  in  the  present  large  high  tension  systems,  due  to  the 
different  types  of  apparatus  which  are  installed.  Contingencies 
which  will  frequently  arise  on  one  system  will  be  infrequent  on 
another.  In  treating  the  subject  then,  it  is  necessary  to  outline  the 
general  type  of  the  system  which  is  to  be  considered,  principally  in 
regard  to  the  apparatus  which  it  serves. 

A  system  may  have  overhead  and  underground  lines  supplying 
step-down  transformers  operating  induction  motor  generators, 
synchronous  motor  generators  or  rotary  converters,  or  it  may  have 
induction  motor  generator  sets  or  synchronous  motor  generator  sets 
directly  connected  to  the  primary  distribution  system.  The  com- 
bination of  nearly  all  these  conditions  is  obtained  in  a  few  large 
high  tension  transmission  systems  now  in  operation  in  some  of  our 
large  cities.  It  is  evident  that  the  contingencies  which  will  arise 
on  such  a  system  will  be  more  varied  than  the  contingencies  arising 
on  a  system  supplying  only  one  class  of  transmission  lines  and  only 
one  type  of  translating  apparatus.  The  system  of  the  Chicago  Edi- 
son Company  and  the  Commonwealth  Electric  Company  is  repre- 
sentative of  the  former  class,  and  as  examples  and  conditions  pre- 
sented throughout  this  paper  will  refer  particularly  to  this  system, 
a  brief  description  of  the  principal  features  relative  to  the  examples 
and  conditions  cited  will  be  given. 

The  high  tension  system  of  the  Chicago  Edison  Company  and  the 
Commonwealth  Electric  Company  consists  of  a  3-wire,  3-phase, 
25-cycle,  9000-volt  primary  distributing  system  fed  with  but  one  ex- 

[238] 


JGASTMAN:     PROTECTING  DISTRIBUTING  SYSTEMS.         230 

ception  by  three-phase  star-wound  generators.  The  system  is  oper- 
ated from  two  generating  plants,  the  Fisk  Street  station  having  at 
present  a  normal  capacity  of  15,000  kilowatts,  and  the  Harrison 
Street  station  having  a  normal  capacity  of  10,000  kilowatts.  The 
neutral  of  the  9000-volt  generators  is  brought  out  and  connected 
to  a  common  ground  bus  in  each  station. 

The  primary  distributing  lines  consist  of  43  lines  of  three-con- 
ductor, paper  insulated,  lead  covered  cable  and  one  overhead  line 
interconnecting  generator  stations  and  sub-stations.  With  few  ex- 
ceptions, the  cables  are  made  up  of  No.  4-0  conductors  with  insula- 
tion of  6/32-in.  paper  concentric  with  the  conductor  and  4/32-in. 
paper  wrapped  over  all,  jute  or  hemp  filler  being  used,  and  the 
whole  treated  with  a  resin  oil.  The  length  of  underground  cables 
connected  to  the  system  is  63  miles.  The  length  of  overhead  lines, 
9.4  miles. 

The  translating  apparatus  in  the  sub-stations  consists  of  9000- 
volt,  3-phase  synchronous  motors  direct  connected  to  60-cycle 
generators;  step-down  static  transformers  operating  rotary  con- 
verters and  step-down  static  transformers  driving  induction  motors 
for  operating  exciter  generators.  A  diagram  of  the  high-tension 
system  is  shown  in  Fig.  1. 

GBOUNDS  ON  THE  SYSTEM. 

In  the  process  of  installing  an  underground  three-conductor 
cable,  the  insulation  wrapped  over  all  the  conductors  is  more  liable 
to  injury  than  the  insulation  concentric  with  each  conductor.  Any 
mechanical  injury  to  the  insulation  concentric  to  the  conductor  is 
generally  confined  to  the  insulation  of  one  conductor  and  is  seldom 
obtained  on  all  three  conductors  at  one  point  in  the  cable.  A  re- 
sultant breakdown  in  insulation  due  to  mechanical  injury  is,  there- 
fore, more  frequent  between  conductor  and  ground  than  between  in- 
dividual conductors.  The  effect  of  electrolysis  is  to  produce  the 
same  result.  As  a  general  rule  a  small  hole  is  first  obtained  in  the 
lead  which  is  nearer  to  one  conductor  than  it  is  to  the  other  two. 
and  the  moisture  entering  causes  a  breakdown  to  ground. 

The  effects  of  grounds  should  be  studied,  and  an  effort  made  to 
determine  the  resultant  effect  which  will  be  produced  by  grounds 
in  all  conceivable  cases,  in  order  that  proper  precautions  may  bo 
taken  to  limit  the  extent  of  injuries  to  the  system. 

On  any  alternating-current  system,  the  relative  potentials  which 


240 


EASTMAN:     PROTECTING  DISTRIBUTING  SYSTEMS. 


exist  between  any  part  of  the  system  and  ground  will  depend  upon 
the  distribution  of  the  electrostatic  capacity  throughout  the  sys- 
tem. The  insulation  resistance  is  necessarily  so  high  that  its  effect 


FIG.  L 


in  determining  the  potentials  which  will  exist  between  the  system 
and  ground  will  not  be  noticeable. 

The  condensance  of  the  system  performs  the  function  of  elastic 
ligaments,  connecting  the  system  to  ground.    The  elastic  limit  of 


EASTMAN:     PROTECTING  DISTRIBUTING  SYSTEMS.         241 

the  ligaments  is  the  potential  at  which  the  dielectric  is  broken  down 
and  a  direct  short-circuit  established.  The  effect  of  a  ground  on 
the  system  depends  upon  the  nature  of  the  ground  and  the  value 
of  its  reactance  in  relation  to  the  condenser  reactance.  An  appre- 
ciation of  the  above  statement  can  be  best  obtained  by  the  pres- 
entation of  a  few  examples  which  might  occur  in  actual  practice. 

The  total  capacity  of  the  overhead  and  underground  transmis- 
sion circuits  of  the  Chicago  system  is  2.79  microfarads  between  two 
conductors,  and  10.64  microfarads  between  each  conductor  and 
ground.  The  capacity  reactance  (condensance)  between  two  con- 
ductors at  25  cycles  equals  2285  ohms,  and  the  condensance  between 
each  conductor  and  ground  is  598  ohms. 


FIG.  2. 

Pig.  2  represents  the  distribution  of  capacity  in  a  three-con- 
ductor underground  cable.  The  lines  representing  the  condenser 
plates  are  drawn  to  scale  so  that  a  relative  comparison  between  two 
conductors  and  between  each  conductor  and  ground  is  graphically 
represented.  It  will  be  noted  that  the  capacity  between  conductor 
and  ground  which  is  the  factor  determining  the  relative  potentials 
which  will  exist  between  ground  and  system  is  several  times  greater 
than  the  capacity  between  conductors. 

The  distribution  of  condensance  in  overhead  lines  is  shown  in 
Pig.  3.  In  this  diagram  it  is  assumed  that  the  line  conductors  are 
properly  transposed  so  that  the  capacity  between  conductors,  con- 
sidering the  entire  system,  is  balanced.  It  wil]  again  be  noted  that 
in  the  overhead  system,  the  capacity  between  each  conductor  and 
ground  is  greater  than  the  capacity  between  conductors. 

It  is  interesting  to  make  a  comparison  between  the  capacity  of 

ELEC.  BYS. —  16. 


242         EASTMAN:     PROTECTING  DISTRIBUTING  SYSTEMS. 

a  system  with  underground  cables  and  the  equivalence  with  over- 
head lines.  If  all  the  lines  of  the  Chicago  system  were  overhead, 
assuming  a  distance  between  conductors  of  16  and  25  ins.  re- 
spectively and  a  height  of  35  ft.  above  ground,  the  total  capacity 
of  the  system  between  two  conductors  would  be  .57  microfarads 
and  between  each  conductor  and  ground  .65  microfarads.  The  con- 
densance  at  25  cycles  between  two  conductors  would  be  11,300  ohms 
and  the  condensance  between  conductors  and  ground  9620  ohms. 
The  ratio  of  capacity  in  the  overhead  system  to  that  in  the  under- 
ground system  would  be  1  to  16.4  between  conductors  and  ground, 
and  1  to  4.9  between  two  conductors. 


FIG.  3. 

Diagram  Figs.  4  and  5  represent  the  arrangement  of  capacity  in 
relation  to  the  three-phase  pressure  diagram.  As  in  Fig.  2  and 
Fig.  3  the  condenser  plates  are  drawn  to  scale,  so  that  a  comparison 
can  be  made  between  underground  system  and  an  equivalent  over- 
head system. 

The  effect  of  a  ground  on  any  conductor  is  to  shunt  the  condens- 
ance of  the  system  between  that  phase  and  ground,  and  it  is  evident 
that  the  relative  potential  which  will  exist  between  the  system  and 
ground  will  depend  upon  the  nature  and  value  of  the  grounding 
impedance  and  the  relation  it  bears  to  the  shunted  condenser 
reactance. 

An  idea  of  the  effect  which  will  be  produced  by  an  inductivo 
ground  can  best  be  obtained  by  an  inspection  of  Fig.  6.  In  diagram 


EASTMAN:    PROTECTING  DISTRIBUTING  SYSTEMS.         -24:', 

Fig.  6  it  is  assumed  that  the  condensance  of  C  phase  is  shunted 
by  inductive  reactance  having  no  resistance  component.  It  will  be 
readily  conceived  that  if  the  inductance  is  equal  to  the  condensance, 
that  the  impedance  of  the  circuit  between  C  and  G  will  be  infinite, 
and  the  relative  potential  to  ground  will  be  determined  by  the 
capacity  between  the  phases  A  and  B.  If  these  two  condensers 
are  of  equivalent  value,  the  ground  will  be  located  at  the  point  Gl 
midway  between  A  and  B,  and  the  potential  from  A  and  B  to 
ground  will  be  one-half  the  delta  potential  of  the  system;  the 


FIG.  4. 

potential  from  G  to  ground  will  be  86.6  per  cent  of  the  delta  po- 
tential of  the  system.  As  the  inductance  is  decreased  it  will  be 
evident  that  the  potential  between  the  system  and  ground  will  be 
increased;  since  the  condensers  between  A  and  B  are  in  series  with 
an  inductive  reactance.  The  potential  will  increase  as  the  induct- 
ance is  decreased,  until  the  latter  is  one-third  of  the  reactance  of 
each  condenser.  For  this  value  of  grounding  reactance,  the  poten- 
tial between  system  and  ground  will  be  infinite.  With  a  further 
decrease  in  the  inductive  reactance,  line  G  G2  will  swing  through 
infinity  and  the  potential  will  decrease  along  the  line  G  G3  until, 
when  the  grounding  reactance  is  zero,  C  will  be  at  ground  potential. 
If  an  inductive  ground  could  be  obtained  having  no  ohmic  com- 


244         EASTMAN:     PROTECTING  DISTRIBUTING  SYSTEMS. 

ponent,  a  ground  of  199  ohms  on  the  underground  system  of  Chi- 
cago would  produce  an  infinite  voltage,  and  if  the  system  were 
overhead,  a  ground  of  3206  ohms  would  produce  the  same  effect. 
Thus,  it  will  be  seen  that  the  factor  which  determined  the  relative 
potential  to  ground  depends  both  on  the  grounding  impedance  and 
the  condensance  of  the  system. 

Fig.  7  is  a  diagram  showing  conditions  which  would  be  obtained 
when  the  ground  is  on  the  primary  of  one  transformer  of  a  star 
connected  set  of  transformers.  The  transformer  on  which  the 


FIG.  5. 

ground  is  obtained  is  connected  between  A  and  the  neutral.  The 
curve  shown  is  plotted  for  a  solid  ground  on  the  primary  for  dif- 
ferent points  along  the  winding.  Condition  m2  would  be  obtained 
when  the  ground  occurred  in  the  center  of  the  transformer.  Con- 
dition ra4  would  be  obtained  when  the  ground  is  on  the  primary, 
one-quarter  the  distance  between  A  and  the  neutral.  AL  repre- 
sents the  pressure  which  would  be  impressed  upon  the  transformer 
when  the  ground  occurred  at  the  center  of  the  primary  winding 
and  GL  and  BL  represent  the  potentials  which  would  be  impressed 
on  the  other  two  transformers. 

Fig.  8  is  a  diagram  of  the  same  conditions,  considering  the  sys- 
tem is  overhead  instead  of  underground.     The  results  shown  in 


EASTMAN:     PROTECTING  DISTRIBUTING  SYSTEMS.         245 

Fig.  7  and  Fig.  8  are  for  transformers  of  200-K.W.  capacity 
each  under  full  load  conditions.  It  will  be  noted  that  a  ground 
under  the  conditions  given  which  would  cause  considerable  trouble 
on  an  underground  system  would  cause  very  little  trouble  on  an 
equivalent  overhead  system.  The  same  potentials  would  prob- 
ably be  obtained  on  an  overhead  system  with  transformers  of  about 
20-K.W.  capacity.  Much  higher  potentials  may  be  obtained  if  at 
the  point  where  ground  occurs  an  arc  is  produced. 

GROUNDING  THE  NEUTRAL  OF  GENERATORS. 
The  remedy  adopted  for  the  Chicago  system  for  eliminating  the 
possibility  of  obtaining  high  potentials  between  the  system  and 


ground  was  the  solid  grounding  of  the  neutral  of  all  the  star- 
wound  generators  in  the  generating  stations.  It  is  universally 
admitted  that  grounding  the  neutral  will  eliminate  the  chances  of 
obtaining  excessive  electrostatic  disturbances  on  the  system.  Fear 
is  expressed  by  some  engineers  that  with  a  grounded  system,  a 
ground  on  the  system  which  directly  becomes  a  short-circuit  be- 
tween neutral  and  one  conductor  of  the  generators  will  result  in 
surging  throughout  the  system,  thereby  producing  results  which 
would  be  as  disastrous  as  the  trouble  which  it  was  aimed  to  elimi- 
nate. In  some  instances  a  resistance  has  been  installed  between 
the  neutral  and  ground  to  limit  the  flow  of  current  to  ground.  It 


246         EASTMAN:     PROTECTING  DISTRIBUTING  SYSTEMS. 

is  hoped  that  in  this  manner  the  short  circuit  could  so  be  damp- 
ened, that  surging  would  not  result.  In  a  large  high-tension  sys- 
tem it  would  be  impracticable  to  install  a  resistance  for  the  purpose 
of  dampening  short-circuit  oscillations,  on  account  of  the  enormous 
current  which  the  resistance  would  have  to  take  care  of. 

It  would  seem  that  a  better  system  would  be  the  operation  of 
only  one  generator  at  a  time  with  the  neutral  grounded,  thus  limit- 
ing the  current  which  would  flov.^on  the  occurrence  of  a  ground 
to  the  short-circuiting  current  capacity  of  that  machine. 

It  should  be  borne  in  mind  that  with  the  occurrence  of  a  short- 
circuit  which  is  limited  to  one  conductor  and  ground,  that  the 


energy  which  is  furnished  the  short-circuit  will  be  supplied  by  the 
generators  in  the  generating  station  and  that  the  synchronous  ap- 
paratus in  the  sub-stations,  unless  their  neutrals  be  grounded  also, 
will  furnish  no  energy  until  the  short-circuit  has  been  translated 
to  between  conductors.  Thus,  if  a  ground  can  be  detected  and  re- 
moved from  the  system  before  fit  has  had  time  to  develop  into  a 
short-circuit  between  conductors,  the  effect  on  the  system  will  be 
greatly  decreased.  In  the  operation  of  the  Chicago  system,  in 
nearly  all  case?  the  short  circuits  in  the  underground  cable  have 
occurred  between  conductor  and  ground,  and  when  the  overload 
relays  were  not  retarded  in  their  action  by  time  limit  devices,  the 
circuits  on  which  the  trouble  has  occurred  have  been  opened  before 
the  short-circuit  was  transmitted  to  other  conductors. 


EASTMAN:     PROTECTING  DISTRIBUTING  SYSTEMS. 


•24] 


GROUND  DETECTORS. 

The  above  fact  has  led  to  the  investigation  of  a  means  for  ob- 
taining a  ground  detector  which  could  be  used  for  the  purpose  of 
indicating  a  ground  or  operating  a  relay  controlling  the  circuit 
breaker  of  the  circuit  on  which  the  ground  occurs.  For  this  pur- 
pose the  Chicago  Edison  Company  is  experimenting  with  a  device, 
a  diagram  of  which  is  shown  in  Pig.  9.  This  device  consists  of  a 
laminated  iron  ring  having  three  independent  windings  of  an  equal 
number  of  turns,  uniformly  distributed  over  the  core,  and  a  fourth 
winding  of  any  desired  number  of  turns  which  is  connected  to  a 
meter  or  relay  for  providing  the  desired  indications.  Each  of  the 
three  similar  windings  is  connected  to  the  secondary  of  a  line  cnr- 

B 


FIG.  8. 

rent  transformer.  So  long  as  there  is  no  escape  of  line  current 
from  the  line  to  ground  the  currents  through  the  three  windings 
will  neutralize  each  other  and  no  flux  will  result  in  the  iron  core. 
As  soon  as  the  ground  is  obtained  part  of  the  current  fed  through 
the  transformer  will  return  to  the  generator  through  the  ground 
and  an  indication  will  be  obtained  by  means  of  the  fourth  winding. 
It  is  hoped  that  by  means  of  this  with  the  combination  of  instan- 
taneous and  time  limit  relays,  the  line  on  which  the  ground  occurs 
will  be  automatically  located  and  its  circuit  breaker  opened  in- 
stantly. In  this  manner  the  ground  may  be  cut  off  before  the 
trouble  has  been  transmitted  to  other  conductors  and  the  trouble 
limited  to  one  line  and  only  that  part  of  the  system  which  is 
affected  by  its  operation. 


248 


EASTMAN:     PROTECTING  DISTRIBUTING  SYSTEMS. 


OVERHEAD  LINES  ON  CONNECTION  WITH  UNDERGROUND  SYSTEM. 

The  introduction  of  an  overhead  line  operating  in  multiple  with 
a  large  system  of  cable  introduces  a  very  hazardous  element  and 
makes  it  necessary  to  safeguard  the  system  against  atmospheric 
charges.  Every  possible  precaution  should  be  taken  with  a  view  of 
preventing  the  transmission  of  a  high  potential  on  the  overhead 
line  to  the  underground  system.  There  is  but  one  overhead  line 
connected  to  the  Chicago  system  and  although  it  has  been  in  service 
only  a  few  months  several  cases  of  trouble  have  occurred  on  it  and 


FIG.  9. 

the  protective  apparatus  installed  has  successfully  prevented  the 
transmission  of  trouble  to  the  underground  system.  This  over- 
head line  is  connected  to  the  bus-bars  at  the  Fisk  Street  station 
through  a  900-ft.  length  of  underground  cable.  At  the  junction 
of  the  underground  cable  and  the  overhead  line,  a  lightning-ar- 
rester house  was  built  in  which  were  installed  choke  coils,  lightning 
arresters  and  a  circuit  breaker  on  the  line.  The  choke  coils  in- 
stalled had  an  inductive  equivalent  of  200  ft.  of  overhead  line. 
Two  banks  of  lightning  arrester  were  installed,  one  being  connected 
to  the  center  of  the  choke  coils  and.  the  other  on  the  overhead  side 
of  the  coils.  Besides  the  line  circuit  breaker  in  the  lightning- 
arrester  house,  a  circuit  breaker  was  installed  in  the  switchhouse. 
Care  was  taken  to  adjust  the  overhead  relays  so  that  in  case  of 
trouble  on  the  line  the  switch  in  the  lightning-arrester  house  would 
be  the  first  to  open. 


EASTMAN:     PROTECTING  DISTRIBUTING  SYSTEMS.         249 

OVERLOAD  RELAYS. 

One  of  the  most  important  parts  affecting  the  control  of  a  high 
tension  system  is  the  overload  relay  which  controls  the  automatic 
opening  of  the  line  circuit  breakers.  Theae  relays  should  be  capa- 
ble of  selecting  the  line  on  which  trouble  occurs  and  opening  the 
line  instantly.  For  this  purpose  a  combination  of  a  time  limit  and 
instantaneous  element  is  necessary,  the  time  limit  feature  being 
set  to  protect  the  cable  or  apparatus  against  dangerous  overloads 
and  the  instantaneous  device  being  adjusted  to  operate  only  in 
case  of  short-circuits  or  grounds.  The  time  limit  devices  which 
have  been  used  without  the  combination  of  these  two  elements 
have  resulted  in  the  operation  of  circuit  breakers  of  lines  on  which 
no  trouble  has  occurred,  in  some  cases  shutting  down  the  entire 
system.  In  laying  out  the  system,  the  application  of  the  overload 
relay  should  be  borne  in  mind  and  wherever  possible  the  lay-out 
should  be  so  arranged  that  each  line  receives  its  energy  either  over 
a  number  of  lines,  or  else  directly  from  the  bus-bars  of  the  generat- 
ing station,  in  this  manner  causing  the  short-circuiting  or  ground- 
ing current  in  the  line  on  which  trouble  occurs  to  exceed  in 
amount  the  current  of  any  other  line  on  the  system.  To  illustrate 
this  point,  referring  to  diagram  Fig.  1  of  the  Chicago  system,  it 
will  be  observed  that  there  are  six  lines  connecting  the  Morgan 
Street  sub-station  to  the  Fisk  Street  generating  station.  In  order 
to  insure  these  lines  remaining  in  service  when  a  short-circuit 
occurs  on  lines  connected  beyond  the  Morgan  Street  sub-station,  it 
will  be  necessary  to  set  the  instantaneous  device  on  the  overload 
relays  for  current  values  so  high  that  the  sum  of  the  currents  in 
all  the  lines  is  in  excess  of  the  short-circuiting  current  which  the 
Fisk  Street  station  is  capable  of  delivering.  The  time  limit  ele- 
ment may  be  set  low  enough  to  protect  the  cable  against  the  con- 
tinuous overloads  which  would  endanger  apparatus  and  affect  the 
normal  operation  of  the  system. 

OIL  CIRCUIT  BREAKERS. 

The  application  of  no  other  device  has  played  such  an  important 
part  in  making  the  operation  of  a  large  high-tension  system  pos- 
sible, as  has  that  of  the  oil  switch.  Experiments  have  shown  that 
with  the  presence  of  electrostatic  capacity  the  open  arc  in  air 
has  very  destructive  effects.  Instances  have  been  obtained  where, 
upon  opening  the  circuit  in  air,  arc  lengths  of  from  20  ft.  to  30  ft. 


230         EASTMAN:     PROTECTING  DISTRIBUTING  SYSTEMS. 

have  been  obtained.  Confining  the  arc  in  oil,  the  phenomenon 
which  is  obtained  with  the  open  arc  apparently  ceases  to  exist. 
This  fact  should  be  borne  in  mind  and  precaution  taken  throughout 
the  system  as  far  as  possible  to  limit  to  a  confined  space  the  short- 
circuiting  arcs  which  are  apt  to  occur.  Every  precaution  should 
be  taken  with  auxiliary  circuits  and  devices  upon  which  the  opera- 
tion of  the  circuit  breaker  depends.  The  opening  of  a  switch  or 
the  falling  back  of  a  switch  into  a  closed  position  may  result  in  as 
much  damage  to  the  system  as  the  most  severe  short-circuit.  The 
switch  should  be  capable  of  successful  operation  through  a  very 
wide  range  in  voltage,  in  order  that  the  control  will  not  be- 
come inoperative  when  trouble  on  the  circuits  causes  a  drop  in 
pressure  of  the  secondary  system. 

PROTECTION  OF  TRANSLATING  APPARATUS. 

The  apparatus  in  the  sub-station  feeding  from  the  primary  dis- 
tribution system  should  be  protected  with  overload  relays  operat- 
ing circuit  breakers,  both  on  the  primary  and  secondary  system. 
With  a  sudden  reversal  of  current  in  either  a  series  or  a  shunt- 
wound  rotary  converter  the  field  is  apt  to  be  weakened  to  an  extent 
such  that  a  dangerous  speed  would  be  obtained.  To  prevent  this, 
a  speed  limit  device  controlling  the  direct-current  circuit  breaker 
should  be  installed.  To  guard  against  the  speeding  up  of  a  rotary 
converter  on  which  the  speed  limit  device  has  failed  to  operate 
and  translating  its  excessive  speed  to  other  synchronous  machines 
in  multiple  with  it,  the  speed  limit  device  should  also  control  the 
operation  of  the  alternating-current  circuit  breakers. 

To  reduce  the  liability  of  obtaining  excessive  speeds  on  convert- 
ers, the  sub-station  translating  apparatus  should  be  arranged, 
wherever  possible,  so  that  rotary  converters  do  not  operate  in  multi- 
ple with  synchronous  motor-generator  sets  connected  to  the  same 
line.  The  opening  of  the  line  switch  in  such  a  case  would  result  in 
the  dropping  out  of  step  of  the  motor,  thereby  causing  the  speed- 
ing up  of  the  rotary  converter  due  to  the  demagnetizing  action  of 
the  heavy  lagging  current  set  up  in  the  rotary  armature. 

In  any  system  care  should  be  taken  to  prevent  the  manual 
operation  from  interfering  with  the  automatic.  The  com- 
bination of  hand  and  automatic  operated  devices  should  be 
avoided  as  far  as  possible,  thus  minimizing  the  tendency  of  the 
operators  to  rely  upon  automatic  devices.  For  example,  when 


EASTMAN:     PROTECTING  DISTRIBUTING  SYSTEMS.         251 

certain  cases  of  trouble  arise  the  automatic  devices  may  be  de- 
prived of  their  means  of  automatic  control  and  hence  fail  to 
perform  their  functions  of  protection.  In  such  a  case  an  at- 
tempt to  operate  these  devices  manually  would  also  result  in 
failure  and  a  loss  in  time  which  may  cause  the  wrecking  of  the 
apparatus  involved,  whereas,  if  the  operator  had  performed  the 
regular  routine  of  manual  operation  independent  of  all  automatic 
devices  the  damage  would  probably  have  been  prevented. 

Every  precaution  should  be  taken  in  the  installation  of  auto- 
matic-controlling devices  to  make  their  operation  independent 
of  the  normal  service  conditions  of  the  system,  thus  insuring 
their  successful  operation  under  any  conditions  which  may  arise. 

In  conclusion,  too  much  stress  cannot  be  laid  on  the  care- 
ful testing  of  all  pieces  of  apparatus  to  be  installed  on  the  sys- 
tem. All  lines  and  apparatus  should  be  periodically  inspected  and 
tested,  and  no  expense  should  be  spared  in  obtaining  correct  ex- 
planations of  the  causes  of  all  trouble  which  arises  on  the  system. 


EOTAEY   CONVEBTEES   AND   MOTOR-GENERA- 
TOR SETS. 


BY   WM.    C.   L.   EGLIN,   Delegate   Association   of  Edison   Illuminating 

Companies. 


In  the  distributing  systems  of  the  electric-supply  companies  in 
the  United  States,  the  demand,  for  low-tension  direct-current 
service  is  usually  of  the  first  importance.  The  distribution  is 
underground  by  means  of  three-wire  network,  fed  from  sub- 
stations located  near  the  load  centers;  the  sub-stations  being  con- 
nected by  means  of  high-tension  alternating-current  feeders  to 
the  main  generating  station,  which  is  located  where  the  best  facili- 
ties are  available  for  economical  operation.  The  sub-stations  are 
usually  provided  with  a  storage  battery,  and  in  some  cases  with 
an  auxiliary  steam  equipment,  which  is  used  in  the  event  of  emer- 
gency or  for  extraordinary  loads  during  the  winter  months.  In 
most  cases,  however,  where  auxiliary  steam  apparatus  is  used,  it 
forms  part  of  an  old  generating  station  which  has  been  changed  to 
a  sub-station. 

The  percentage  of  the  total  load  converted  for  direct  current 
varies  widely  in  different  localities,  and  in  the  larger  supply 
companies  it  varies  from  30  per  cent  to  100  per  cent.  Some  of 
the  leading  companies  also  supply  power  to  the  sub-stations  of 
street  railway  companies,  and  others  have  a  500-volt  power  cir- 
cuit, although  most  of  the  direct  current  is  supplied  on  three-wire 
230-volt  systems. 

In  all  cases  the  percentage  of  the  total  load  converted  from 
alternating  current  to  direct  current  is  large,  so  that  an  effective, 
reliable,  and  efficient  means  of  transforming  alternating  current 
to  direct  current  is  essential.  The  three  methods  available  for 
this  purpose  are  rotary  converters,  motor-generator  sets,  and  recti- 
fiers, the  first  two  only  of  which  are  available  at  present  for  trans- 
forming large  currents. 

KOTARY    CONVERTERS. 

A  rotary  converter  is  similar  to  a  direct-current  generator, 
with  taps  made  on  the  armature  winding  and  the  addition  of 

[252] 


EGLIN:     CONVERTERS  AND  MOTOR-GENERATOR  8ET8.     253 

collector  rings  to  introduce  alternating  current.  In  a  single 
phase  rotary  converter  these  taps  would  be  made  180  deg.  apart; 
for  two-phase,  90  deg.,  and  similar  arrangements  for  polyphase 
systems.  In  most  of  the  larger  rotary  converters  using  three-phase 
systems,  the  phases  are  split  so  as  to  use  six  phases  on  the  rotary 
converter,  and  in  that  way  increase  the  capacity  of  the  machine. 
The  efficiency  of  the  rotary  converter  is  higher  than  of  the  direct- 
current  generator,  for  the  reason  that  part  of  the  current  passes 
directly  through  the  windings.  The  rotary  converter  must  be  oper- 
ated in  synchronism  with  the  generator,  and  when  started  from 
the  alternating-current  side  has  all  the  characteristics  of  a  syn- 
chronous motor.  The  rotary  converter  may  be  either  shunt-wound 
or  compound-wound.  The  voltage  at  the  direct-current  end  of  the 
shunt-wound  type  depends  upon  the  voltage  of  the  alternating  cur- 
rent delivered  to  the  collector  rings,  and  practically  cannot  be 
varied  without  varying  the  alternating  current  impressed  on  it. 
Varying  the  field  strength  has  the  effect  of  changing  the  power 
factor,  making  the  current  either  leading  or  lagging  without  materi- 
ally changing  the  voltage  delivered  on  the  direct-current  end.  This 
necessitates  some  form  of  regulator  on  the  alternating-current  side 
so  as  to  control  the  voltage  on  the  direct-current  end  of  the  rotary. 
There  are  two  methods,  either  the  introduction  of  induction  regu- 
lators in  the  alternating-current  leads  on  each  phase  of  the  rotary, 
or  dial  switches  on  the  step-down  transformers,  which  vary  the 
ratio  between  the  primary  and  secondary  winding.  The  step-down 
transformers  are  arranged  so  as  to  deliver  the  proper  voltage  for 
the  e.m.f.  desired  on  the  direct-current  side  of  the  rotary;  and, 
therefore,  a  rotary  converter  equipment  consists  of  step-down  trans- 
formers, regulators,  and  the  rotary  converter,  with  the  necessary 
switches  and  safety  devices. 

Means  must  be  provided  for  starting  the  rotary  converter  and 
bringing  it  to  synchronous  speed.  The  rotary  may  be  started  from 
either  end,  preferably  from  the  direct-current  side.  When  starting 
from  the  alternating-current  side,  the  current  required  exceeds  the 
full-load  current  usually  from  50  to  100  per  cent;  and  some  means 
must  be  provided  for  controlling  this  large  current;  also  the  field 
must  be  cut  out  until  synchronous  speed  is  obtained. 

When  started  from  the  direct-current  side,  the  machine  is  started 
similar  to  the  direct-current  motor  with  variable  resistances  in  the 
armature  circuit,  which  is  gradually  cut  out  as  the  machine  accel- 
erates in  speed.  The  rotary  is  then  synchronized  with  the  alternat- 


254      EGLIN:      CONVERTERS  AND   MOTOR-GENERATOR  SETS. 

ing-current  generator  similar  to  the  operation  of  paralleling 
alternators.     Starting  arrangements  may  be  common  for  a  number 
of  rotaries,  and  this  is  arranged  for  by  switches  on  the  switchboard. 

A  third  method  which  has  been  used  on  large  rotary  converters 
is  the  starting  motor,  using  an  alternating-current  motor  of  the  in- 
duction type  to  bring  the  machine  up  to  synchronous  speed.  When 
only  one  rotary  converter  is  in  use,  and  direct  current  is  not  avail- 
able for  starting,  and  the  rotary  is,  therefore,  started  from  the 
alternating-current  side,  care  must  be  exercised  to  test  the  polarity, 
as  it  is  very  probable  it  may  be  reversed.  This  can  usually  be  recti- 
fied by  opening  the  switch  on  the  alternating-current  side,  allowing 
the  machine  to  slip  a  pole. 

The  rotary  converter  meets  all  of  the  commercial  conditions 
demanded  of  it,  and  is  capable  of  delivering  current  on  the  direct- 
current  side  at  from  110  to  600  volts.  It  can  be  operated  on  varying 
frequencies  from  25  to  60  cycles  successfully.  Rotary  converters 
operate  better  at  the  low  frequencies  for  reasons  which  will  be  dis- 
cussed later. 

In  the  early  introduction  of  rotary  converters,  difficulties  were 
met  which  were  principally  due  to  hunting,  usually  caused  by 
variations  in  the  angular  velocity  of  the  generator.  This  caused 
a  swing  action  of  the  revolving  part  of  the  rotary  converter, 
which  generally  increased  unless  some  means  were  provided  to 
dampen  this  effect.  The  effect  of  hunting  causes  excessive  spark- 
ing at  the  brushes,  and  when  hunting  becomes  excessive  the  ma- 
chine will  flash  over  at  the  commutator  and  short-circuit  the  di- 
rect-current side  of  the  machine;  and  unless  safety  devices  are 
provided  the  machine  is  liable  to  be  destroyed.  The  difficulty  of 
hunting  has  been  overcome  by  the  addition  of  bridges  between 
the  poles  of  the  machine.  The  design  of  these  bridges  was  capable 
of  being  varied  so  as  to  increase  the  dampening  effect  required. 
The  first  form  was  a  copper  bridge  placed  between  the  poles,  but 
it  was  found  that  additional  dampening  effect  was  required. 
The  poles  were  then  undercut  and  copper  bridges  were  extended 
under  the  pole  tips.  The  most  powerful  form  consisted  of  a  cop- 
per bridge  imbedded  in  the  pole  face.  The  addition  of  bridges 
usually  reduced  the  efficiency  of  the  machine;  rarely,  however, 
exceeding  1  to  H  per  cent.  The  proper  remedy  for  hunting  is 
naturally  the  removing  of  the  cause  by  obtaining  a  uniform  rota- 
tion of  the  generator,  which  can  be  accomplished  by  the  combina- 
tion of  an  effective  governor  and  the  necessary  fiy-wheel  effect  on 


EGLIN :     CONVERTERS  AND  MOTOR-GENERATOR  SETS.     255 

the  engine.  Hunting  does  not  seem  to  take  place  when  the  gen- 
erators are  driven  by  either  steam  or  water  turbines.  A  number 
of  rotary  converters  have  failed  owing  to  the  killing  of  the  field, 
due  either  to  the  circuit  being  open  or  to  the  effect  upon  the  field 
caused  by  disturbances  on  the  alternating-current  side,  thus  al- 
lowing the  machine  to  exceed  its  normal  speed,  or,  in  other  words, 
run  away.  These  failures  have  required  the  installation  of  aux- 
iliary apparatus  and  of  safety  devices,  which  are  usually  installed 
as  follows: 

A  circuit-breaker  on  the  direct-current  side  arranged  to  trip  with 
excessive  overload,  which  cuts  out  the  rotary  in  the  event  of 
its  flashing  over  at  the  commutator;  and  speed-limiting  devices  to 
trip  the  circuit-breakers  on  the  alternating-current  and  direct- 
current  sides.  In  some  cases  the  alternating-current  side  of  the 
rotary  is  provided  with  an  overload  and  reverse-current  circuit- 
breaker  which  trips  when  the  current  is  reversed;  or,  in  other 
words,  when  the  rotary  is  running  inverted,  supplying  alternat- 
ing current  to  the  line  and  taking  direct  current  from  the  sub- 
station. 

There  are  a  number  of  different  forms  of  speed-limiting  devices, 
both  electrical  and  mechanical.  One  form  of  electrical  de- 
vice consists  of  a  differential  relay,  one  set  of  coils  being  connected 
to  the  alternating-current  bus  and  the  other  set  to  the  collector 
rings.  In  the  event  of  the  rotary  exceeding  its  speed,  the  fre- 
quency at  the  collector  rings  will  increase,  causing  an  unbalance 
at  the  relay  and  tripping  the  circuit-breakers.  The  mechanical 
devices  usually  consist  of  some  governor  attachments  which  make 
contact  in  the  event  of  the  shaft  running  above  its  normal  speed 
and  tripping  the  circuit-breakers.  Various  arrangements  of  the 
field  wiring  so  as  to  allow  combination  separate  and  self-exciting 
connections  have  been  tried  so  as  to  prevent  errors  on  the  part 
of  the  operators. 

The  study  of  the  rotary  converter  from  an  operating  stand- 
point early  indicated  that  the  machine  had  a  high  inherent  effici- 
ency; that  the  voltage  and  load  could  be  easily  regulated  and  the 
power  factor  adjusted  to  suit  the  best  operative  conditions  of  the 
system,  and  that  the  first  cost  of  the  outfit  was  comparatively  low. 
For  these  reasons  it  was  extensively  used,  especially  for  frequen- 
cies of  2  a  cycles. 


256      EGLIN:      CONVERTERS  AND  MOTOR-GENERATOR  SETS. 

MOTOR-GENERATOR  SETS. 

Before  the  rotary  converter  had  been  fully  developed,  a  num- 
ber of  these  machines  were  installed  on  systems  with  frequencies 
of  60  cycles;  and  at  this  frequency  the  difficulties  due  to  hunting 
were  greatly  increased,  and  in  some  cases  satisfactory  operation 
could  not  be  obtained.  This  led  to  the  introduction  of  the  motor- 
generator  sets.  The  first  motor-generator  sets  were  installed  so 
as  to  obtain  the  most  reliable  equipment  irrespective  of  the  cost 
or  efficiency.  These  equipments  consisted  of  a  low-voltage  poly- 
phase induction  motor,  direct  connected  to  either  one  or  two  di- 
rect-current generators  mounted  upon  a  common  base.  The  mo- 
tors were  arranged  with  stationary  coils  and  squirrel  cage  wind- 
ing on  the  rotor,  and  they  were  similar  in  most  respects  to  the 
small  motors  which  have  been  used  successfully  for  a  variety  of 
purposes.  The  generators  were  of  standard  design  and  the  mo- 
tors were  built  to  suit  the  speed  of  the  generator ;  the  motor  being 
supplied  with  low-voltage  current  from  step-down  transformers. 
On  account  of  using  induction  type  motors  the  difficulties  due  to 
hunting  were  removed,  and  the  operation  in  the  sub-station  was 
further  simplified  by  having  no  electrical  communication  between 
the  direct  and  alternating-current  sides,  thus  removing  the  dangers 
of  the  machine  running  away. 

The  motor-generator  sets  can  be  started  either  from  the  direct 
or  alternating-current  side,  by  using  the  generator  as  a  motor  and 
placing  a  variable  resistance  in  the  armature  circuit  similar  to 
the  method  used  in  starting  the  rotary  converter.  When  the  set 
is  started  from  the  alternating-current  side,  some  current-limiting 
device  is  introduced  in  the  alternating-current  circuit  leading  to  the 
motor.  It  has  been  found  of  advantage  in  practice  to  synchronize 
the  larger  motor-generator  sets  so  as  to  prevent  any  sudden  rush 
of  current  when  throwing  the  motors  on  the  system.  As  the 
usual  methods  of  synchronizing  are  not  suitable  for  this  purpose, 
a  disc  with  white  and  black  stripes  is  attached  to  the  shaft  and 
with  an  arc  lamp  connected  to  the  alternating-current  bus,  the 
set  can  be  readily  synchronized  and  at  synchronous  speed  the 
black  and  white  stripes  are  readily  visible.  By  the  attachment  of 
mirrors  to  the  pillow  blocks  of  the  various  motors,  each  set  can 
readily  be  synchronized  by  the  switchboard  attendant.  Bringing 
the  machine  to  synchronous  speeds  is  not  essential,  although  it  is 
recommended  for  the  larger  size  units;  that  is  to  say,  machines  of 


EGLIN:      CONVERTERS  AND  MOTOR-GENERATOR  SETS.     2r>7 

400  kw  or  larger.  It  has  been  found  advantageous  to  start  both 
generators  and  rotary  converters  from  the  direct-current  side  with 
a  starting  bar  operated  by  hand,  thus  reducing  the  amount  of  cur- 
rent required  to  overcome  the  friction  of  rest  about  one-half.  This 
is  often  important  when  the  sub-station  is  heavily  loaded  and  the 
current  is  drawn  from  it  to  start  additional  machines.  It  also  re- 
duces the  size  of  the  starting  resistance ;  for  example,  400-kw  motor- 
generator  sets  or  rotary  converters  may  require  from  400  to  600 
amperes  to  start  them  from  rest,  providing  the  machines  have  been 
standing  for  some  time,  and  thus  the  oil  allowed  to  squeeze  out  be- 
tween the  bearing  and  the  shaft.  With  the  assistance  of  the  start- 
ing bar  this  current  can  be  cut  down  to  200,  and  not  exceeding  250 
amperes  at  230  volts. 

The  operation  of  these  motor-generator  sets  was  all  that  could 
be  expected  of  them  and  was  satisfactory  in  all  respects;  but,  on 
account  of  their  inefficiency  and  high  first  cost,  improvements  were 
demanded. 

A  very  rational  step  was  the  abolishment  of  step-down  trans- 
formers and  the  substitution  of  a  high-tension  for  the  low-tension 
winding  on  the  motors ;  the  introduction  of  one  250  to  300-volt  gen- 
erator instead  of  two  125  to  150-volt  generators,  and,  in  some  cases, 
the  substitution  of  a  synchronous  motor  for  an  induction  motor. 

The  use  of  the  high-tension  winding  on  the  motor  removed  the 
necessity  for  and  cost  of  the  step-down  transformers,  and  more  than 
compensated  for  the  additional  floor  space  required  by  the  motor- 
generator  set.  Regulators  on  the  alternating-current  side  were  un- 
necessary —  the  voltage  on  direct-current  generators  being  readily 
controlled  by  a  rheostat  on  the  shunt  field  —  and  the  operation 
was  simplified,  allowing  the  equipment  to  be  handled  by  the  regular 
class  of  dynamo  operators,  this  being  of  great  importance  in  large 
systems,  as  it  requires  less  time  to  train  the  operators.  Disturbances 
on  the  alternating-current  side  of  the  system  have  little  effect  on  the 
motor-generator  sets  and  are  of  such  a  character  that  they  are  easily 
provided  for  by  protecting  devices. 

The  objection  to  motor-generators,  especially  those  of  induction 
type,  is  the  low-power  factor,  which  increases  the  losses  in  the 
feeders.  The  losses  in  the  feeders  are  usually  a  small  part  of  the 
total  loss,  so  that  this  in  many  cases  is  not  important. 

The  first  cost  of  motor-generator  sets  is  usually  somewhat  higher 
than  of  rotary  converters,  particularly  in  the  large  sizes.  The 

ELEC.  BYS. — 17. 


258     EGLIN:     CONVERTERS  AND  MOTOR-GENERATOR  SETS. 

actual  difference,  however,  is  not  so  great  as  is  generally  supposed. 
The  relative  costs  of  the  various  sizes  are  shown  in  the  following 
table: 

COMPARATIVE  TABLE  or  COSTS. 

notaries  with  trans-       Synch.  Ind.  Synch.  Ind. 

formers  and  regs.        Mt.  Gen.      Mt.  Gen.     Mt.  Gen.      Mt.  Gen. 

25  Cyc.  60  Cyc.  25  Cyc.  25  Cyc.  60  Cyc.  60  Cyc.          Capacity. 

1.00  1.05       1.05       1.10          1.03  1.08           1,000  kw 

1.00  1.00       1.05       1.05          1.00  1.00            500  kw. 

1.00  .95       1.00         .95            .95  .95  250  to  300  kw. 

This  is  based  on  quotations  by  the  same  manufacturer  of  rotary 
converters  and  motor-generator  sets  of  25  and  60  cycles,  with  a  25- 
cycle  rotary  converter  with  transformers  and  regulators  as  a  unit. 

The  following  table  shows  the  efficiency  of  a  400-kw,  60-cycle  ro- 
tary converter  and  a  400-kw  60-cycle  motor-generator  set  with  both 
high  and  low-voltage  motors.  These  tests  were  made  at  the  works 
of  the  manufacturers,  and  show  that  even  at  high  frequencies  the 
rotary  converter  is  more  efficient  than  the  motor-generator  set : 

Rotary  Converter. 

Two-phase,  16  poles,  400  kw,  450  r.p.m.,  230  to  300  volts  rotary. 
Two-phase,  60  cycles,  5000  volts  primary,  210  to  160  volts  sec- 
ondary transformer. 

Per  Cent.  Combined  Efficiency. 

Load.  at  210  Volts.        at  160  Volts. 

100  89.6  90.5 

75  88.0  88.9 

50  84.3  85.5 

25  73.0  75.3 

Motor-Generator  Sets. 

Direct  current,  10  poles,  400  kw,  450  r.p.m.,  125  to  150  volts. 
Alternating  current,  16  poles,  560  kw,  450  r.p.m.,  380  volts. 

Per  Cent.  Combined  Efficiency 

Load.  at  150  Volts. 

100  82.0 

Direct  ojurent,  10  poles,  400  kw,  450  r.p.m.,  230  to  300  volts. 
Alternating  current,  16  poles,  560  kw,  450  r.p.m.,  220  volts. 

Per  Cent.  Combined  Efficiency 

Load.  at  300  Volts. 

100  84.9 


EGLL\  .-    C-OA  r/;y,'7'/-;A'.s  AAL>  MOTOR-GENERATOR  SETS.    259 

Direct  current,  10  poles,  400  kw,  450  r.p.m.,  230  to  300  volts. 
Alternating  current,  16  poles,  560  kw,  450  r.p.m.,  5500  volts. 

Per  Cent.  Combined  Efficiency 

Load.  at  300  Volts. 

100  86.9 

After  these  machines  were  installed  in  the  suh-stations,  a  series 
of  tests  were  made,  using  the  same  observers  and  the  same  instru- 
ments (the  instruments  being  checked  between  tests),  so  as  to 
obtain  the  all-day  efficiencies  when  operating  under  commercial 
conditions;  the  rotary  converters  being  placed  in  one  sub-station 
and  the  motor  generators  in  another,  but  both  supplied  from  the 
same  generating  station.  It  would  appear  from  these  tests  that  there 
is  no  practical  difference  in  the  commercial  efficiency  between  the 
high-voltage  motor-  generator  set  and  the  rotary  converter,  and,  as 
was  to  be  expected,  the  low-voltage  motor-generator  set  was  the 
most  inefficient. 


ALL-DAY  EFFICIENCIES  UNDER  COMMERCIAL  CONDITIONS. 

—  Power  Factor.— 


No.  1 


No. 


No.  3 


Type  of  Mach  ne. 

Load. 

H.  P. 

Eff. 

A  Ph. 

CPh 

Av. 

f  Ind.  Motor 

Empty 

0 

0.0 

0 

.0 

45.9 

23.0 

1  Two-phase 

1/4 

140 

72.9 

67 

.1 

86.4 

76.7 

j  H.  P.,  560 

1/2 

280 

82.1 

83 

.6 

92.8 

88.2 

|  Volts,  220 

3/4 

420 

85.3 

86 

.4 

90.4 

88.4 

[  Amp.,  1150 

Full  Ld. 

560 

85.4 

88 

.7 

92.1 

90.4 

'  Ind.  Motor 

Empty 

0 

0.0 

3.9 

29.1 

16.5 

Two-phase 

1/4 

140 

72.7 

56.9 

69.7 

63.3 

H.  P.,  560 

1/2 

280 

81.2 

77.4 

82.5 

80.0 

Volts,  6000 

3/4 

420 

84.7 

82.5 

86.2 

84.3 

Amp.,  47 

Full  Ld. 

560 

85.9 

85.6 

88.9 

87.3 

Rotary  1/4 

Two-phase         1/2 
KW,  400  3/4 

Volts,  250  Full  Ld. 


134  70.9 

268  77.2 

402  80.4 

536  84.1 


99.2 

100.5 

97.4 

97.6 


106.0  102.6 

105.1  102.8 
102.4  99.9 

98.0  97.8 


CONCLUSIONS. 


The  type  of  machine  to  be  installed  in  sub-stations  depends 
principally  upon  the  frequency  of  the  system  and  the  importance 


-00     EGLIN:     CONVERTERS  AND  MOTOR-GENERATOR  SETS. 

of  reliable  and  continuous  service.  The  frequency  to  be  used  de- 
pends upon  other  conditions  which  are  outside  the  scope  of  this 
paper. 

In  cases  where  the  largest  percentage  of  the  output  of  the  gener- 
ating station  is  to  be  transformed  to  low-tension  direct  current, 
25-cycle  rotary  converters  should  be  installed  on  account  of  their 
higher  efficiency  and  lower  first  cost.  The  very  large  number  of 
these  machines  which  are  now  in  successful  operation  proves  con- 
clusively their  reliability  and  effectiveness.  In  mixed  systems,  and 
where  the  percentage  of  current  transformed  for  low-tension  dis- 
tribution is  small,  motor-generators  are  desirable.  With  higher  fre- 
quency, particularly  60  cycles,  it  has  been  shown  that  motor  gener- 
ators compare  favorably  in  efficiency  and  are  much  more  reliable 
and  simple  in  their  operation. 

DISCUSSION. 

CHAIRMAN  FERGUSON:  Mr.  Eglin's  paper  is  now  ready  for  discussion. 
You  know  that  in  Europe  motor  generator  sets  are  used  very  much  more 
extensively  than  in  this  country,  and  we  shall  be  glad  to  hear  from  any  of 
our  European  friends  as  to  their  experience.  Col.  Crompton,  we  will  be 
glad  to  hear  from  you. 

Col.  R.  E.  B.  CROMPTON:  I  am  unable  fully  to  discuss  this  important 
subject  as  I  have  not  studied  the  paper  sufficiently  carefully  but  I  can  com- 
municate one  figure  which  appears  important  —  that  is,  that  in  the  large 
London  system  with  which  I  have  most  experience,  where  we  generate 
and  transmit  at  5000  volts  transformed  by  motor  generator  sets  to  400  volts, 
and  charge  batteries  through  these  sets;  the  total  losses,  including  those 
in  the  high-pressure  mains,  motor  transformers,  accumulators,  low  pressure 
mains  to  consumers,  amount  to  27  per  cent  as  a  maximum,  but  about 
25  per  cent  on  the  average.  If  we  used  rotary  transformers,  these  losses 
would  be  greatly  reduced. 

Mr.  PHILIP  TOECHIO:  In  comparison  with  the  efficiency  obtained  from 
motor-generator  sets,  I  would  say  that  with  25-cycle  rotary  converters  of 
500  to  1000-kw  capacity,  in  American  cities  the  all-day  efficiency  is  above 
90  per  cent. 

Mr.  M.  J.  E.  TILNEY:  The  writer  mentions  that  he  only  starts  up  from 
the  direct-current  side,  owing  to  the  heavy  starting  current.  There  is  a 
large  system  in  London  where  they  start  up  from  the  high-tension  side, 
with  resistance  in  the  rotors,  and  they  find  the  maximum  current  never 
exceeds  the  full-load  current  of  the  machine,  and  in  many  cases  is  only 
60  per  cent.  Is  there  any  special  advantage  in  starting  from  the  direct- 
current  side? 

Mr.  PHILIP  TORCHIO:  I  want  to  add  another  point,  and  emphasize  a 
matter  that  Mr.  Eglin  touched  upon  in  the  paper,  but  in  my  opinion,  did 
not  dwell  upon  strongly  enough ;  that  is,  the  advantage  oi  the  greater 


EGLIN:      CONVERTERS  AND   MOTOR-GENERATOR  KETti.     2(51 

capacity  you  get  from  a  rotary  converter  than  from  a  motor  generator  set 
for  overload  conditions.  This  is  an  important  factor  in  laying  out  the 
reserve  capacity  for  a  sub-station. 

Mi-.  EGLIN:  The  figure  given  by  Col.  Crompton  is  similar  to  the  figure 
in  this  country  on  motor-generator  sets.  As  to  the  question  of  cutting 
down  the  starting  current,  it  is  not  the  practice  in  this  country  to  start 
from  the  alternating  side.  As  the  motor-generator  sets  are  started  from  the 
direct-current  side,  the  starting  current  would  be  much  smaller  than  60  per 
cent  of  the  full-load  current  of  the  motor.  It  would  not  exceed  25  per  cent. 
The  motor-generator  sets  are  started  in  the  same  way  as  the  rotary  con- 
verters are  started,  using  the  generator  as  a  motor. 


THE  BOOSTER  MACHINE  IN  TRACTION  SER- 
VICE, AND  ITS  PROPER  REGULATION. 


BY  PROF.  DR.  GUSTAV  RASCH. 


In  power  stations  for  electric  railways,  especially  for  those  feed- 
ing a  network  having  a  small  number  of  cars  running  at  the  same 
time,  there  is  a  demand  for  a  device  to  steady  the  power-station 
service.  The  unsteady  load  and  current  consumption  in  such 
power-stations  grows  worse  as  fewer  cars  are  running  at  the  same 
time  on  the  line.  It  is  known  that  ammeters  and  voltmeters  of 
small  power-stations  indicate  fluctuations  continually,  while  large 
power-stations  show  mostly  a  steady  load  with  small  variations 
only.  The  disadvantages  of  the  unsteady  service  with  regard  to 
the  efficiency  and  the  life  of  the  steam-engines  and  the  generators 
of 'the  power-stations  are  obvious.  It  is  desirable  also  that  the  cars, 
especially  those  cars  running  on  the  outer  ends  of  the  line,  be  fed 
with  a  constant  voltage,  which,  however,  cannot  be  expected  from 
a  power-station  having  too  heavily  fluctuating  a  load.  To  steady 
the  machine  service,  a  buffer  storage  battery  is  often  used;  that  is, 
a  floating  battery  connected  parallel  with  the  power-station  genera- 
tors. It  is  indisputable  that  such  batteries  possess  valuable  features. 
For  instance,  they  are  of  great  importance  in  case  of  breakdown 
of  the  machine  service  and  they  give  a  chance  to  run  some  cars 
just  before  starting  up  and  after  shutting  down  the  regular  power- 
station  service.  They  have  a  disadvantage,  however,  in  that  they 
do  not  react  upon  the  fluctuations  of  the  current,  but  only  upon 
the  voltage.  Though  an  absolutely  steady  voltage  on  the  bus  cannot 
be  assumed,  it  is  evident  that  the  battery  does  less  work  as  a  buffer 
battery  the  steadier  the  voltage.  It  is  very  likely,  however,  that 
even  with  nearly  steady  voltage  the  machine  may  be  subject  to 
heavy  fluctuations. 

The  following  discussion  may  explain  these  phenomena  still  more 
cloarly.  The  generator  at  the  railway  power  station  is  shunt- 
wormd,  and,  to  simplify  the  discussion,  it  may  be  assumed  that 

[262] 


RASCH:  BOOSTERS  IN  TRACTION  8ERVIC3. 


263 


the  e.m.f.=  E,  may  drop  proportionally  with  rising  current 
/!  that  is  may  follow  the  law  E~EQ  —  I^c  where  EQ  is  the  elec- 
tromotive force  with  no  load,  and  c  a  constant.  The  constant  c, 
may  cover  the  influence  of  the  armature  reaction  and  the  drop  of 
speed  of  the  machine  with  increasing  current  71.  It  has  evidently 
the  character  of  a  resistance.  The  armature  resistance  of  the 
machine  is  r  (Fig.  1).  The  parallel  connected  buffer  battery  may 


F..      t1 


FIG.  1. 

have  an  electromotive  force  A  and  an  internal  resistance  a.  The 
heavy  fluctuating  current  in  the  network  (the  actual  line  current) 
is  I,  while  It  and  72  are  the  currents  of  the  machine  and  the  storage 
battery. 

It  is  easy  to  derive  the  formula, 


^,  -  A  +  al 
a  +  c  +  r 


.     _(c 
'• 


I- 


-  A) 


(2) 

a  +  c  -T-  , 

At  the  average  value  7m  of  the  actual  line  current,  the  current 
of  the  storage  battery  must  reach  zero  value,  so  that  the  battery 
may  not  be  either  overloaded  or  underloaded  during  daily  service. 
That  is,  following  equation  (2) : 

o  =  (c  +  r)  lm—(E0—A),OT, 

That  changes  the  equations  (1)  and  (2)  to 


and, 


(4) 


It  is  necessary  to  make  ample  estimate  of  /m. 

The  equation  (3)  shows  that  an  absolute  steadying  of  the  machine 


2(U       RASCR:  BOOSTERS  IN  TRACTION  SERVIGE. 

current  7X  is  impossible,  because  it  is  not  independent  of  the  heavy 
liuctuating  actual  current  /.  The  larger  the  value  of  c  +  r,  and 
smaller  the  value  of  a,  the  larger  will  be  the  dampening  effect.  The 
first  means  high  internal  resistance  and  large  drop  of  voltage, 
features  of  the  generators  which  cannot  be  called  desirable  ones. 
A  small  storage  battery  resistance  a,  means  plates  of  large  surface, 
that  is  expensive  cells. 

The  buffer  machine  (booster)  is  another  means  of  steadying  the 
service.  The  value  of  such  a  machine,  especially  for  hoisting  in- 
stallations, was  thoroughly  treated  in  a  paper  by  Mr.  Meyersberg,* 
read  at  the  meeting  of  the  Institution  of  Gorman  Electrical  Engi- 
neers. It  is  indisputable,  however,  that  these  machines  are  also  of 
great  value  for  all  railway  central  stations,  and  for  all  similar 
services  with  load  fluctuations  of  shprt  duration. 

A  large  centrifugal  mass  is  driven  by  an  electric  motor  (under 
certain  conditions  two  motors  may  suitably  be  used).  The  arma- 
ture of  the  motor  is  in  multiple  with  the  network.  The  centri- 
fugal mass  naturally  accumulates  energy  with  decreasing  network 
current  and  gives  out  energy  in  the  network  with  increasing  current 
consumption.  Therefore  the  buffer  machine  works  at  one  time 
as  a  motor,  and  at  another  time  as  a  generator.  For  the  moment 
we  will  not  consider  the  character  of  the  field  excitation  of  this 
machine.  It  will  be  the  object  of  this  paper,  however,  to  calculate 
the  most  favorable  device  for  one  special  case. 

It  may  be  assumed  that  the  actual  current  I,  of  a  600-volt  power 
station  for  a  small  railway  is  the  subject  of  regular  fluctuations 
from  500  to  200  amperes  inside  of  periods  of  12  seconds.  The 
condition  regarding  the  regularity  of  the  sequence  of  the  fluctua- 
tions is  of  minor  importance;  it  is  important,  however,  that  the 
utmost  data  be  obtained  regarding  the  fluctuation  itself;  that  is, 
500  and  200  amperes  be  not  increased  or  decreased,  because  other- 
wise the  buffer  machine  would  be  forced  to  run  at  a  speed  which 
would  not  agree  with  the  speed  which  was  assumed  when  designing 
the  machine. 

The  curve  ABODE  (Fig.  2),  shows  the  actual  current 
fluctuation  inside  of  one  period.  The  average  current  of  the  gen- 
erator ought  not  to  be 

200  4-  500 
— IL =  350  amperes, 

1.  Meyersberg,   Elektrotechnische  Zeitschrift,   1903,   page  261. 


RASCH:     BOOSTERS  IN  TRACTION  SERVICE. 


265 


but  somewhat  higher,  about  360  amperes,  on  account  of  the  efficiency 
of  the  buffer  machine,  which  is  naturally  below  100  per  cent.  With 
absolutely  equalized  service  the  generator  would  work  continuously 
with  this  amount  of  current.  One  may  be  satisfied,  however,  in 
practice  to  limit  the  fluctuations  to  10  per  cent  above  and  below 'this 
amount.  We  therefore  assume  that  the  generator  current  Ig  must 
be  dampened  by  means  of  the  buffer  machine  to  the  limits  of 
fluctuations  between  400  and  320  amperes  (see  curve  At  7?x  C^ 
DI  EI  in  Fig.  2).  Now  then,  7g  -f  7p  =  7,  and  it  follows  that 
the  buffer  current  7p  =7  —  I  g.  The  curve  Az  B2  C2  Z>2  E2  Fig. 
2,  shows  the  work  of  the  buffer  current  7  .  The  positive  values 
mean  taking  energy  (charging),  the  negative  values,  giving  out 
energy  (discharging)  by  the  buffer  machine.  For  the  moment,  the 
e.m.f.  may  be  assumed  as  constant,  at  600  volts,  the  output  of  the 

Ampere  D 


Seconds 

FIG.  2. —  OUTPUT  OF  GENEBATOB  AND  BUFFEB. 

buffer  machine  being  a  maximum  during  charging: 

600   (320  — 200)=  72,000  watts. 

This  value  may  be  used  as  specific  for  the  designing  of  the  buffer 
machine,  though  naturally  there  is  the  intermittent  service  to  be 
taken  care  of  in  addition. 

The  curve  ABODE  (Fig.  3),  shows  the  period  of  loading  and 
unloading  the  buffer  machine.  This  figure  shows  a  time  phase 
retardation  against  Fig.  2,  inasmuch  as  the  period  starts  with 
the  beginning  of  the  load.  It  shows  that  the  loading  has  a  dura- 
tion of  6.54  seconds,  and  the  unloading  a  period  of  duration  of 
5.46  seconds.  The  energy  consumption  is, 
72,000 

2 

The  energy  output  is: 
60,000 


X  6.54  =  236,000  watt-seconda. 


X  5.46  =  164,000  watt-seconds. 


260 


RASGH:  BOOSTERS  IN  TRACTION  SERVICE. 


The  total  efficiency  is  therefore  assumed  as 

164.°00  =0.695 
236,000 

corresponding  to  an  efficiency  of 

yT695  =  .834 

for  the  single  conversion  of  electric  energy  to  mechanical  energy, 
or  vice-versa.  If  a  lower  average  current  of  the  generator  were  to 
be  assumed,  the  efficiency  would  be  proportionately  higher.  It  may 
be  practical  to  reckon  with  more  than  83.5  per  cent  efficiency; 
which  was  purposely  not  done,  however,  for  the  reason  to  be  men- 
tioned in  the  latter  part  of  this  paper. 


BO 

70 
60 
60 
40 
90 
20 
10 
0 
10 
20 
80 
40 
60 

B 

X 

x-" 

Ci 

-\ 

x. 

4WW 

80000 
20000 
10000 

I 

/ 

'V 

\ 

// 

V 

\ 

\ 

DI 

^ 

fr 

\ 

S, 

A! 

/ 

\ 

Ea 

/ 

\ 

/ 

\ 

/ 

V 

E 

A 

\ 

i 

0      1 

1  / 

\ 

/ 

\ 

/ 

\ 

/ 

\ 

/ 

r 

2 

FJQ.  3. —  ENERGY  AND  POWER  OF  BUFFER. 

We  will  not  define  how  much  of  the  energy  stored  in  the  centri- 
fugal masses  is  to  be  used,  but  state  only  that  at  the  end  of  an 
unloading  period  there  has  still  to  be  stored  an  energy  L%+  mkg 

This  energy  storage  will  be 

T       r  ^    »<u  236'000 

i  =  ie+.83      -5-^- 

That  is, 

(5)  L  =  Le  +  20,000  mkg. 

If  U  is  the  highest  speed  per  minute,  we  have 
(G)     L  =  c  Uz,  c  being  a  constant,  the  value  of  which  i?  of  no 


RASCH:     BOOSTERS  IN  TRACTION  SERVICE.  267 

interest  at  this  place  in  the  discussion.    If  (1  —  s)  U  is  the  smallest 
allowable  speed  of  the  fly-wheel  (s  being  the  slip),  we  will  have 

(7)  Le=c    (1  —  *)2  (72 
from  (6)  and  (7)  may  be  derived: 

(8)  ^=(i_,)t 

JL/ 

and  in  connection  with  (5),  we  may  write: 

(9)  Z-  20'000< 

The  amount  of  slip  s  is,  therefore,  of  fundamental  influence. 
Large  values  of  s  (for  instance  s  =  .5)  allow  the  use  of  relatively 
small  fly-wheels,  the  specification  for  which  is  determined  by  the 
value  of  L.  On  the  other  hand,  however,  the  reserve  of  energy  is 
very  small  with  large  slip.  On  the  end  of  a  normal  unloading 
period,  the  vis-  viva  of  the  fly-wheel  has  diminished  to  : 

-$•  100  =100  (1  —  s)  2  per  cent  of  the  starting  value.     This  rep- 
JU 

resents  the  reserve  for  exceptionally  large  unloading,  decreasing 
with  increasing  slip,  as  shown  by  the  following  table: 

s  =  .2  .3  A  .5 


Another  reason  against  increasing  the  slip  is,  that  the  dimen- 
sions of  the  buffer  machine  increase  with  low  speed.  With  large 
slip,  however,  the  average  speed  will  be  .lower  than  with  small  slip. 

Remembering,  therefore,  that  large  slip  calls  for  small  centri- 
fugal masses  only,  but  for  large  buffer  machines,  and  vice-versa,  and 
that  small  slip  calls  for  large  centrifugal  masses  and  small  buffer 
machines,  it  is  evident  that  the  proper  amount  of  slip  to  be  chosen 
is  one  of  the  problems  which  come  up  often  in  engineering,  —  that 
is  to  find  out  the  conditions  under  which  the  sum  of  the  first  cost  of 
two  parts  of  a  machine  is  a  minimum.  This  problem,  however,  is 
not  to  be  solved  generally,  but  can  be  solved  only  in  each  case,  by 
approximation,  giving  due  weight  to  all  practical  questions.  We 
will  not  dwell  upon  this  problem,  but  assume  that  we  did  find  as 
most  favorable  value,  s  =  .3.  That  would  give  us,  following  the 
equation  (9),  the  maximum  vis-  viva 

L  —  39,200   mkg. 
Incidentally  at  this  place  may  be  answered  the  question  why 


208  RASCH:     BOOSTERS  IN  TRACTION  SERVICE. 

special  buffer  machines  are  used  instead  of  using  heavier  centrifugal 
masses  hin  •connection  with  the  generator  itself.  This  question 
answers  itself,  if  one  observes  the  fact  that  in  the  latter  case  the 
slip  would  not  be  more  than  5  per  cent;  for  s  =  .05,  however,  it 
follows  from  equation  (9)  that 

L==  £05,000  mkg. 

Assuming  the  same  peripheral  speed  of  the  fly-wheels,  the  weights 
of  the  fly-wheels  are  proportional  to  the  vis-viva,  and,  to  get 
the  same  effect,  the  fly-wheel  connected  to  the  generator  would 
have  to  be  made  five  times  as  heavy  as  that  driven  by  the  buffer 
machine. 

Returning  to  Fig.  3  and  choosing  a  scale  for  the  vis-viva,  we 
may  draw  on  this  scale  the  ordinate: 

A  A1  =  Le  =  39,200  (1  —.3)  2=  19,200  mkg. 
The  loading  time  (AC  Fig.  3)  amounting  to  6.54  seconds  is  to  be 
divided  in  two  parts  of  3.27  seconds  each.  In  the  first  part  the 
energy  put  into  the  fly-wheel  per  unit  of  time  is  increasing,  while 
in  the  second  part  it  is  decreasing.  The  effect  transmitted  to  the 
buffer  machine  in  the  first  part  of  the  period  at  the  time  t  is  : 

72,000      t      watts. 
3.27 

The  amount  of  energy  accumulated  in  the  fly-wheel  at  this  time 
t  is: 

Zt==  19,200  +    l221     !il^°  Ct  dt  =  19,200  +  935  **  mkg. 
9.  8  1        3.27    J  o 

This  gives  us  the  means  of  calculating  the  several  ordinates  of  the 
curve  Al  B^.  Following  the  same  formula,  the  vis-viva  at  the 
end  of  the  first  part  of  the  loading  time  is  found  to  be  29,200  mkg. 
For  the  second  part,  a  similar  simple  calculation  results  in, 

7<t=29,200  +  935  (£  —  3.27)   (9.81  —  t) 

where  t  is  increasing  from  3.27  to  6.54  seconds.  The  develop- 
ing of  the  formula  for  the  vis-viva  with  unloading  fly-wheel  may 
be  derived  in  a  similar  way.  It  should  be  considered,  however,  that 
the  efficiency  of  the  buffer  machine  is  to  be  regarded  as  the  divisor 
of  the  expression.  For  the  third  interval: 

6.54  "<  t~<  9.27,  we  have 

-  -    -J  _    6-M 
0.834X9.8-1       2.73 

=  39,200  —  1340  (t—  6.54)2. 


=  39,200  -  -    -     _     -  c-  6.54) 

0.834X9.8-1       2.73   J  6.54 


RASCH:     BOOSTERS  IN  TRACTION  SERVICE.  200 

This  course  is  shown  in  curve  Cr  DL.    In  the  fourth  interval  there  is, 

9.27  _<  t  <  12  and  Lt  =  19,200  +  1340  ( 12  —  t) 2. 
interval. 

The  curve  A^  B^  Cl  Dl  E^  Fig.  3,  shows  the  course  which  the 
vis-viva  has  to  follow  if  the  buffer  machine  is  to  regulate  in  the  way 
shown  in  Fig.  2. 

The  next  question  is :  How  is  the  speed  to  be  changed  in  order 
to  get  this  course  of  the  vis-viva.  We  have  to  follow  the  earlier 
mentioned  equation  (6), 

L  =  c  U2. 

It  refers  to  the  maximum  value  of  the  vis-viva  and  speed,  but 
may  be  used  just  as  well  for  every  other  value.  Thus  substituting 
L  t  and  Uv  we  obtain  : 

(10)  Lt=c  Uf. 

From  the  equations  (6)  and  (10), 
Jt.    ITT   ^ 


L      '    ^' 


One  is  not  limited  in  the  choice  of  maximum  speed.  The 
weight  0  (kg),  the  peripheral  speed  v  (  -  -7  j  and  the  vis-viva 
L,  are  (  a  plain  cylindrical  fly-wheel  being  assumed)  in  the  relation, 


4  X  9.81  * 

With  a  peripheral  speed  of  45  m.  per  sec.,  there  is,  therefore, 
L  =  39,200  and  £  =  760  kg. 

In  order  to  avoid  too  large  fly-wheel  weight,  it  is  suitable  to  use 
a  high  peripheral  speed.  Speeds  of  60  m.  per  second,  and  over, 
have  been  proposed  for  fly-wheels  of  suitable  construction.  There 
still  remains  the  choice  of  speed.  It  is  not  necessary  to  determine 
now  the  exact  number  of  revolutions.  It  is  sufficient  to  assume  as 
maximum  value 

Z7=100 

and  to  express  the  different  values  of  speed  in  per  cents  of  this 
maximum  value.  From  the  values  found  for  the  vis-viva  the 
necessary  number  of  revolutions  are  derived,  shown  in  the  curve 
A  B  C  D  E  in  Fig.  4.  The  load  of  the  buffer  machine  is  transferred 


270 


RASCH:     BOOSTERS  IN  TRACTION  SERVICE. 


to  this  figure  from  Fig.  3.  It  is  to  be  seen  that  the  buffer 
machine  has  its  highest  load  at  a  moderate  number  of  revolutions, 
—  (in  our  case  86.3  per  cent). 

It  was  assumed  that  the  voltage  on  the  busses  was  constant 
Naturally  this  does  not  apply  in  practice;  it  will  decrease  with 
increasing  current  consumption,  and  vice-versa.  Therefore,  it  will 
be  higher  when  loading  the  buffer  machine  than  with  unloading. 
That  is,  the  storing  of  energy  while  loading  the  buffer  machine  will 
be  favored;  the  unloading  on  the  other  hand  will  interfere  with 


K..W.                                                                                    U-Vott 

70 
60 
SO 
40 
90 
20 
20 
0 
10 
JO 
80 
40 
60 
60 

B 

A 

/ 

x^ 

Cj 

^x 

D2 

C90 
620 
610 
600 
690 
58ft 
570 

/ 

'V 

/ 

V 

N 

1 

& 

\ 

/ 

' 

\ 

\ 

A8 

1  / 

\ 

/ 

/ 

D,\ 

\ 

\ 

/ 

/ 

\ 

v  / 

/C2 

\ 

E 

^. 

^ 

/ 

\ 

\ 

"  — 

1 

\\ 

N/1 

' 

\ 

E] 

/ 

B2 

\ 

E 

A 

j 

C\J 

1 

}  i 

1   / 

\ 

/ 

\ 

/ 

\ 

/ 

\ 

/ 

\ 

2 

FIG.  4.  —  ENEBQY  AND  POWEE 


D 

OP  BUFFER. 


the  giving  up  of  energy.  Unsteady  voltage  will  have  the  same 
influence  as  a  resistance  in  the  armature  circuit  of  the  buffer 
machine,  resulting  in  a  lower  efficiency,  which  was  chosen  rather 
low  for  this  reason.  The  question  is  now  to  decide  upon  the 
factors  which  could  be  used  to  improve  the  regulation: 
These  are, 

(1)  The  voltage, 

(2)  Buffer  current  7p, 

(3)  The  actual  line  current  7, 

(4)  The  generator  current  7  , 

(5)  The  speed. 

The  same  objections  hold  true  for  the  voltage,  which  have  been 
developed  in  the  discussion  of  the  buffer  battery.     If  the  buffer 


RASCH:     BOOSTERS  IN  TRACTION  SERVICE. 


271 


machine  is  simple  shunt  wound,  it  will  be  influenced  by  the  voltage. 
This  would  not  allow  the  regulation  of  such  heavy  fluctuations  as 
defined  in  our  above  calculations,  and  the  energy  consumption  and 
the  restoration  of  energy  by  the  fly-wheel  would  take  place  within 
much  narrower  limits. 

Fig.  5  shows  that  the  current  of  the  buffer  machine  cannot  be 
used  for  regulating  purposes.  Fig.  5  is  derived  from  Fig.  4,  using 
load  and  unloading  current  as  abscissa,  and  the  desired  revolutions 
per  minute  as  ordinates.  The  curve  shows  that  to  any  value  of 
the  current  there  belong  generally  two  different  values  of  the  speed, 


Discharge 

U     Charge 

^ 

-**" 

100 

| 

-^ 

X 

\ 

\ 

/ 

\ 

\ 

/ 

\ 

V 

> 

< 

70 

Giip 

—  >• 

re 

100    80 
i     i 

60     40      20      0       20     40      60 
Buffer  current 

80     100    120 

600  ' 
t         I 

Jo    '    400    '    360    '    820    '    280 
Line  current 

\         I         I            t           l 

'    240    '   J» 

IB 

880                3GO                     840 
Generators  current 

FIG.  5. 

»         B> 

the  difference  of  which  is  the  greater  as  the  current  is  lower.  Ob- 
viously, this  condition  is  not  to  be  reached  in  practice.  However, 
we  may  influence  the  regulation  by  the  current,  one  value  of  it  will 
always  call  for  only  one  definite  value  of  the  speed.  The  same 
considerations  regarding  the  buffer  current  holds  true  also  for  the 
actual  line  current  and  for  the  generator  current.  To  Fig.  5  are 
added  values  of  the  actual  and  generator  current,  which  prove 
in  this  case  that  a  suitable  regulation  cannot  be  reached,  since 
one  of  them,  decreasing  or  increasing  according  to  the  network 
current  load,  cannot  produce  two  different  speeds  of  the  buffer 
machine.  It  would  be  possible  to  influence  the  field  of  the  buffer 
machine  by  the  combined  buffer  current  and  line  current,  in  ad- 
dition to  a  special  shunt  winding  fed  from  the  bus,  but  even  this 
would  not  give  the  correct  result.  We  wish  to  transmit  the  fluctua- 


272       RASCH:  BOOSTERS  IN  TRACTION  SERVICE. 

tions  of  the  line  current  to  the  buffer  current,  which  means  that  both 
of  them  must  reach  their  highest  values  simultaneously,  as  shown 
in  Fig.  2.  The  two  currents  working  in  two  different  windings  on 
the  magnet  field  of  the  buffer  machine  would,  according  to  the 
way  they  were  connected,  work  either  with  or  against  each  other. 
In  the  first  case  they  would  not  reach  the  desired  result;  in  the 
second  case,  the  result  would  be  equal  to  that  which  could  be 
reached  with  one  of  the  currents  alone,  which  is  not  suitable,  as 
above  mentioned. 

The  question  of  making  use  of  a  change  in  speed  for  regulating 
the  buffer  effect  gives  us  two  possibilities : 

(1)  Using  a  centrifugal  regulator  to  adjust  a  rheostat  placed  in 
the  field  winding  of  the  buffer  machine. 

(2)  The  use  of  a  special  exciter  machine  driven  from  the  buffer 
machine,  and  having  therefore  a  speed  proportional  to  that  of  the 
buffer  machine.2 

The  latter  seems  to  be  the  most  favorable,  since  this  regulation 
is  not  applied  step  by  step,  but  gradually. 

We  assume  again  a  steady  voltage  on  the  bus,  and  assume  further- 
more that  the  e.m.f.  of  the  buffer  machine  with  maximum  current 
varies  from  5  per  cent  above  to  5  per  cent  below  this  voltage ;  in  this 
case  the  vibration  of  e.m.f.  during  the  period  of  12  seconds  is 
shown  in  the  curve  Az  B2  C2  D2  E2  (Fig. '4).  The  proportion  of 
the  ordinates  of  this  curve,  and  of  the  curve  ABODE  —  that  is 

E       E  M.F. 
U  ~  ~   speed 

are  proportional  to  the  lines  of  force  which  are  necessary  for  the 
field  of  the  buffer  machine  to  produce  the  desired  regulation.  Fig. 
6  shows  a  diagram,  the  abscissae  of  which  are  proportional  to  the 

V 

value     =,  and  the  ordinates  proportional  to  the  speed.   In  this  case 

there  are  also  generally  two  ordinates  for  one  abscissa,  but  the  dif- 
ference in  the  most  unfavorable  case  is  8  per  cent,  while  the  regula- 
tion by  means  of  the  currents  showed  differences  of  30  per  cent 
(Fig.  5).  If  both  branches  of  Fig.  6  could  be  combined  —  which 
would  call  for  no  armature  resistance  whatever  in  the  buffer  ma- 
chine —  the  regulation  would  be  a  perfect  one.  We  remark,  there- 
fore, that  a  low  armature  resistance  is  favorable. 

2.  Both  kinds  of  regulation  are  the  subject  of  the  German  patents  No. 
129,553,  assigned  to  the  German  General  Electric  Co.,  Berlin. 


KASCH:     BOOSTERS  IN  TRACTION  SERVICE. 


273 


The  connections  may  be  as  follows  (Fig.  7)  : 

The  buffer  machine  P  is  provided  with  two  field  windings  Mt  and 

a.    M l  ia  excited  from  the  busses ;  M 2  from  a  small  generator  e, 


100 
90 
80 
TO 

5 

^ 

\ 

\ 

\ 

\ 

\ 

\ 

^ 

J>    6.0             7.0             8.0             9. 

FIG.  6. 

placed  upon  the  axle  of  the  buffer  machine,  and  excited  from  the 
bus  also.  The  windings  Mt  and  M2  are  differentially  connected, 
so  that  with  increasing  current  in  Jf2,  the  total  field  of  the  buffer 
machine  will  be  weakened. 

Another  arrangement  would  be  to  use  a  part  of  the  winding  M 


FIG.  7. 

as  the  second  winding  M2,  as  shown  in  Fig.  8.  The  latter  arrange- 
ment has  the  advantage  of  a  smaller  winding  space  necessary  for 
the  buffer  machine ;  it  has  the  disadvantage,  however,  that  the  small 
machine  e  has  eventually  to  be  designed  for  rather  high  voltages, 
while  with  an  arrangement  according  to  Fig.  7,  voltage  and  current 
of  the  small  generator  may  be  chosen  at  will. 

ELEC.  RYS. 18.  . 


274 


RASCH:  BOOSTERS  IN  TRACTION  SERVICE. 


The  small  generator  may  also  be  designed  as  motor,  the  arma- 
ture of  which  is  to  be  connected  in  series  with  the  magnet  winding 
M  of  the  buffer  machine  (Fig.  9).  In  this  case  increasing  the  speed 
of  the  buffer  machine  will  cause  an  increase  of  the  e.m.f.  of  the 


FIG.  8. 

small  machine,  and  result  in  decreasing  the  exciter  current  of  the 
buffer  machine.  In  all  arrangements,  while  working,  there  is  a 
weakening  of  the  field  of  the  buffer  machine,  and,  therefore,  the  di- 
mensions of  these  machines  must  be  made  ample,  in  comparison 
with  other  machines  of  the  same  average  load.  We  may  mention 


FIG.  9. 

that  in  all  cases  the  maximum  armature  current  of  the  buffer 
machine  does  not  reach  its  highest  value  at  the  same  time  with  the 
weakest  field,  but  with  an  average  strong  field,  which,  of  course,  is 
favorable. 

The  discussion  has  shown  that  the  most  suitable  regulation  of  the 
buffer  machine  is  to  be  effected  by  means  of  speed  regulation. 


STORAGE  BATTEEIES  IN  ELECTEIC  RAILWAY 

SERVICE. 


BY  JUSTUS  B.  ENTZ. 


The  principal  applications  of  batteries  to  electric  railway  systems 
are  made  at  the  generating  stations,  at  distributing  sub-stations,  and 
directly  connected  to  points  on  a  direct-current  distributing  line. 
The  objects  of  such  installations  are  to  store  electrical  energy  at 
efficient  and  convenient  periods  and  to  return  it  when  most  useful, 
generally  at  periods  of  increasing  or  heavy  load.  A  storage  bat- 
tery, which  is  a  reservoir  of  electrical  energy,  when  connected  to  the 
circuit,  makes  the  conditions  of  generation  and  transmission  up  to 
the  point  where  the  battery  is  connected  independent  of  the  load 
demand  of  the  circuit  beyond  that  point.  The  storage  battery  also 
permits  the  rate  of  production  of  energy  to  be  independent  of  the 
rate  of  demand.  The  demand  for  electric  current  may  occur  at  a 
time  when  its  production  will  be  inconvenient  or  inefficient,  or  both, 
The  demand  may  call  for  a  very  high  rate  of  output  for  a  short 
time,  as  in  electric  railway  systems,  where  the  maximum  demand 
lasts  only  for  a  period  of  a  few  seconds.  By  the  use  of  a  battery  the 
rate  of  producing  energy  may  be  adjusted  with  reference  to  other 
considerations,  such  as  efficiency  of  generating  apparatus.  This 
energy  may  be  produced  at  low  and  constant  rates  and  stored  in  a 
battery  and  given  out  to  meet  the  demands  of  variable  and  very 
high  rates.  The  results  thus  obtained  are  improved  efficiency  of 
operation  and  greater  reliability  of  service. 

In  comparing  a  battery  with  the  generating  and  transmission  ap- 
paratus, it  will  be  noted  that  the  battery  handles  most  economically 
those  portions  of  the  load  which  are  least  economical  for  generating 
or  transmission  apparatus,  namely,  those  which  are  of  extremely 
short  duration  and  excessive  in  amount,  as  well  as  those  which  are 
of  considerable  duration,  but  of  very  small  amount.  The  maximum 
economy  of  usefulness  is  secured  by  such  division  of  load  between 
the  battery  and  other  apparatus  that  each  handles  that  portion  to 
which  it  is  best  adapted. 

[275J 


270        ENTZ:     ELECTRIC  RAILWAY  STORAGE  BATTERIES. 

The  reasons  for  installing  storage  batteries  in  railway  work  are 
as  follows : 

1).  Keasons  affecting  investment. 

2).  Reasons  affecting  economy  of  operation. 

3).  Reasons  affecting  reliability  and  public  convenience  and 
safety. 

It  is  impossible  to  draw  a  sharp  line  between  the  three  classes  of 
reasons.  A  part  of  the  total  investment  for  railway  equipment  is 
made  for  economy  or  for  reliability.  The  consideration  of  a  bat- 
tery in  this  class  of  work  usually  involves  the  comparison  of  bat- 
tery with  generating  machinery,  or  in  some  cases  the  transmission 
copper  and  sub-station  equipment,  or  with  all  of  them  on  the  three 
headings  enumerated  above.  In  such  a  comparison  the  following 
points  must  be  considered : 

1).  The  results  of  the  comparison  of  investment  will  depend 
upon  the  shape  of  the  load  diagram  and  upon  the  methods  and  dis- 
tances of  transmission  and  upon  what  portion  of  the  load  is  as- 
signed to  the  battery.  In  general,  however,  it  may  be  stated  that 
there  is  almost  invariably  some  portion  of  the  maximum  load  which 
may  be  carried  by  a  battery  at  an  investment  cost  not  exceeding 
that  for  the  apparatus  it  actually  displaces  to  do  the  same  work. 
It  is  often  sound  engineering  to  increase  the  proportion  of  the  bat- 
tery considerably  beyond  that  point  to  secure  more  fully  the  ad- 
vantages in  headings  2  and  3 ;  and  it  must  be  borne  in  mind  that 
many  of  the  functions  of  a  battery  can  be  performed  by  no  other 
class  of  apparatus,  and  where  these  functions  are  vital,  the  invest- 
ment comparison  is  of  minor  importance. 

2).  Under  the  head  of  economy  of  operation  must  be  included 
both  generation  and  transmission  of  energy  and  both  labor  and  fuel 
economy,  as  well  as  cost  of  maintenance  and  depreciation.  As 
loads  of  certain  nature  are  handled  more  economically  by  the  bat- 
tery than  by  generating  machinery,  the  maximum  fuel  economy  is 
secured  by  such  division  of  load  between  the  battery  and  machinery 
that  each  handles  that  portion  for  which  it  is  best  adapted. 

The  question  of  the  size  of  a  power  equipment  is,  of  course, 
confined  to  a  determination  of  the  requirements  necessary  to  meet 
the  maximum  load  conditions,  whereas,  considering  economy  of 
operation,  the  average  load  conditions  must  be  considered.  In  the 
sub-station  there  is  an  increased  efficiency  of  rotaries  and  trans- 
formers due  to  the  operation  of  batteries  which  must  be  compared 
with  the  losses  in  the  battery.  With  the  batteries  used  very  con- 


ENTZ:     ELECTRIC  RAILWAY  STORAGE   BATTERIES.      -277 

eiderably  on  peak  work,  their  output  will  amount  to  from  15  to 
20  per  cent  of  the  total  output  of  the  station.  As  the  hattery 
under  average  conditions  will  not  be  fully  used,  but  a  certain  por- 
tion of  it  held  in  reserve  to  meet  abnormal  conditions,  the  efficiency 
of  the  battery  will  be  high.  Taking  this  at  85  per  cent  as  a  mini- 
mum, we  find  that  the  losses  in  the  batteries,  where  their  output  is 
20  per  cent  of  the  total,  is  3  per  cent  of  the  total  output  of  the 
system. 

It  is  safe  to  say  that  on  account  of  the  improved  efficiency  in 
transmission  and  the  improved  load  factors  on  the  rotaries,  the 
efficiency  of  the  sub-station  should  be  increased  by  considerably 
more  than  this  amount,  and  that  any  improved  economy  in  the 
generation  of  power  at  the  main  power-house  will  be  net  gain. 

The  economies  at  the  power-house  from  the  operation  of  bat- 
teries will  be  such  as  to  produce  ideal  economy  in  both  boiler  and 
engine-room.  The  load  on  the  engines  and  boilers  can  be  adjusted 
to  practically  the  24-hour  average,  and  need  be  varied  only  when 
this  average  is  changed.  With  peaks  in  the  morning  and  evening 
to  double  the  height  of  the  average  load,  this  will  mean  operating 
through  the  day  at  practically  one-half  the  capacity  that  will  be 
needed  at  the  peaks  without  the  battery.  To  handle  these  peaks 
without  the  battery,  it  would  be  necessary  to  keep  one-half  of  the 
total  boiler  capacity  with  fires  banked  from  18  to  20  hours  a  day 
for  operation  during  the  hours  of  peaks.  The  constant  loss  in  these 
boilers  through  radiation  and  the  escape  of  heated  gases  would 
probably  not  be  less  than  20  per  cent  of  their  capacity;  and  one- 
half  of  these  losses,  or  10  per  cent  of  the  boiler  capacity  required 
with  the  battery  in  service,  would  be  saved.  This  would  mean  a 
saving  of  10  per  cent  of  the  total  fuel. 

The  improved  load  factor  on  the  engines  and  generators  and  the 
reduction  in  the  number  of  engine  hours  of  operation  would  effect 
an  additional  economy.  There  is  a  considerable  loss  of  steam  when 
every  unit  is  started  up,  this  being  the  steam  consumed  from  the 
time  the  throttle  is  opened  to  the  time  the  load  is  thrown  on  the 
generator.  As  the  operation  of  batteries  would  reduce  the  number 
of  times  the  unit  is  started  up  and  shut  down,  there  would  be  a 
saving  on  this  point.  I  believe  that  it  would  be  conservative  to 
expect  a  saving  on  this  point  of  from  5  per  cent  to  10  per  cent, 
making  a  total  saving  of  fuel  in  the  operation  of  a  power  plant  with 
batteries  of  from  15  to  20  per  cent. 

It  has  been  stated  that  a  storage  battery  is  a  good  thing  to  patch 


278        UNTZ:     ELECTRIC  RAILWAY  STORAGE  BATTERIES. 

up  bad  engineering.  This  is  true,  and  there  is  a  considerable  field 
for  its  application  in  this  way.  It  is,  however,  not  limited  to  such 
cases,  and  is  often  the  only  means  of  preventing  engineering  prov- 
ing to  be  bad  owing  to  the  impossibility  of  foretelling  what  con- 
ditions are  to  be  met  exactly.  The  extreme  flexibility  of  a  battery 
in  meeting  conditions  varying  over  a  very  wide  range  renders  it 
peculiarly  applicable  to  such  cases. 

Under  the  question  of  maintenance  and  depreciation  it  may  be 
noted  that  with  a  storage  battery  these  two  items  are  combined  in 
one.  The  renewals  of  plates  which  are  made  from  time  to  time 
keep  the  battery  up  to  date,  so  that  at  the  end  of  a  period  of  years 
it  is  not  an  obsolete  piece  of  apparatus,  but  it  is  up  to  date  in  every 
respect  and  equal  to  the  batteries  then  in  the  market,  including  all 
the  improvements  in  plate  construction  which  have  been  introduced 
since  it  was  installed.  The  flexibility  of  the  battery  to  meet  changes 
in  conditions,  such  as  desirability  of  increased  voltage  or  larger 
capacity,  is  also  to  be  noted,  such  changes  in  conditions  often  in- 
volving the  discarding  of  generating  apparatus;  whereas  in  a  bat- 
tery, the  simple  modification  in  the  number  of  cells,  or  the  number 
of  plates  in  each  cell,  will  suffice. 

3).  The  reliability  of  the  storage  battery  and  its  absolute  freedom 
from  break-down  without  warning  is  due  in  part  to  the  fact  that 
it  is  composed  of  a  multitude  of  small  units,  each  unit  being  a  bat- 
tery plate,  any  one  of  which  can  be  put  out  of  service  without 
noticeably  affecting  the  operation  of  the  entire  installation ;  whereas, 
in  a  generating  plant,  the  various  parts,  such  as  boilers,  engines, 
generators,  switchboard  apparatus,  transmission  lines,  transformers, 
and  converters,  are  all  connected  in  series  and  the  derangement  of 
any  one  class  of  these  parts  instantly  interrupts  completely  the 
operation  of  the  whole.  The  deterioration  of  a  battery  is  in  all 
cases  very  gradual,  and  repairs  can  be  made  without  taking  the 
battery  out  of  service. 

As  an  emergency  reserve,  the  battery  can  be  found  of  immense 
value  in  any  one  of  the  following  ways : 

a).  In  case  of  a  total  shut-down  of  the  power-house  or  high-ten- 
sion lines,  the  amount  of  battery  which  would  usually  be  installed 
from  other  considerations  would  be  sufficient  to  maintain  the  en- 
tire service  of  the  road  at  the  time  of  the  peak  for  three-quarters  to 
one  and  one-half  hours,  or  for  twice  as  long  during  the  middle  of 
the  day,  thus  permitting  temporary  repairs  to  be  made.  In  case  of 
un  interruption  of  longer  duration,  the  battery  would  at  least  CD- 


ENTZ:     ELECTRIC  RAILWAY  STORAGE   BATTERIES.        270 

able  the  trains  to  be  run  into  the  station  and  the  passengers  dis- 
charged, instead  of  leaving  them  stalled  between  stations. 

b).  At  a  sub-station  the  rotaries  could  be  shut  down  for  an  in- 
definite period  of  time,  the  battery  being  floated  on  the  line  at  a 
somewhat  reduced  voltage. 

c).  The  batteries  are  available  instantly  to  take  care  of  sudden 
excessive  load  of  short  duration,  due  to  any  unusual  congestion  of 
traffic. 

d).  They  will  take  care  of  and  prevent  interruptions  from  short- 
circuits  on  the  line  which  would  otherwise  fall  on  the  machines, 
saving  overloading  them  and  then  throwing  out  the  breakers  and 
interrupting  the  traffic. 

e).  The  batteries  would  permit  the  entire  machinery  of  the  power- 
house and  sub-station  to  be  shut  down  at  night  and  the  current  cut 
off  the  alternating-current  lines  for  a  period  of  several  hours  for 
repairs  and  inspection. 

/) .  The  batteries  would  often  make  it  possible  to  purchase  either 
alternating  or  direct  current  from  other  systems  at  times  when  they 
were  not  overloaded,  and  at  a  constant  and  controllable  rate  which 
would  cause  no  disturbance.  This  power  could  be  utilized  on  the 
system  at  times  of  peak  load,  when  it  probably  could  not  be  pur- 
chased. 

The  fact  that  the  batteries  are  available  in  case  of  emergency 
would  permit  the  shutting  down  of  machinery  when  signs  of  trouble 
first  appear,  thus  reducing  the  extent  of  the  damage  which  might 
be  caused  by  continuing  to  run  partially  disabled  machinery  until 
a  substitute  could  be  put  in  service. 

The  points  enumerated  above  apply  to  batteries  installed  at  the 
power-house  and  those  installed  on  the  line.  Certain  additional  ad- 
vantages arise  in  many  cases  from  installing  a  battery  at  some  dis- 
tance from  the  source  of  power,  due  to  the  improved  conditions  of 
transmission.  With  such  a  battery,  it  becomes  necessary  to  trans- 
mit only  the  average  power  required  instead  of  the  maximum.  The 
result  will  be  a  saving  in  the  amount  of  copper  required  for  a  given 
drop  in  voltage,  or  an  improvement  in  the  voltage  with  a  given 
amount  of  copper,  or  the  advantages  may  be  divided  between  the 
two  methods.  An  increase  in  economy  will  also  be  secured,  since 
it  is  a  well-known  fact  that  to  transmit  a  given  amount  of  energy 
over  a  certain  conductor  in  a  given  time,  with  a  minimum  loss,  the 
rate  of  transmission  should  be  constant. 

The  installation  of  a  storage  battery  at  a  generating  station  is 


280        ENTZ:     ELECTRIC  RAILWAY  STORAGE  BATTERIES. 

to  take  the  peak  of  the  load  for  its  maximum  two  or  three  hours, 
and  to  regulate  or  control  the  rapid  fluctuations  of  load  occurring 
all  day.  Where  the  station  voltage  has  not  a  drooping  character- 
istic it  is  necessary  to  add  to  the  voltage  of  the  battery  the  voltage 
of  an  auxiliary  generator,  in  order  to  cause  it  to  discharge  at  the 
time  and  by  the  amount  necessary.  This  auxiliary  generator,  com- 
monly called  a  booster,  also  serves  for  charging  the  battery  without 
varying  the  bus-pressure  of  the  station  by  adding  its  voltage  to  that 
of  the  bus,  the  armature  of  the  booster  being  in  series  with  the  bat- 
tery and  its  field  strength  being  automatically  controlled  where  the 
changes  of  load  are  at  all  rapid.  When  located  at  some  distance 
from  the  power-house,  the  booster  may  be  dispensed  with,  as  the 
variation  in  the  line  voltage  will  be  sufficient  to  cause  the  battery  to 
do  its  work.  Located  in  this  way  the  battery  will  maintain  the 
voltage  on  the  line  at  approximately  its  average  point.  If  the  num- 
ber of  cells  in  the  battery  are  properly  adjusted  to  float  this  aver- 
age voltage,  the  battery  will  remain  in  the  same  average  state  of 
charge.  If  the  average  voltage  at  the  point  where  a  line  battery  is 
located  is  found  too  low  for  satisfactory  results,  a  booster  may  be 
installed  at  the  power-house  and  sufficient  current  transmitted  over 
a  feeder  direct  to  the  battery  at  a  voltage  higher  than  the  bus  to 
maintain  the  battery  voltage  at  the  desired  point,  this  latter  arrange- 
ment affording  means  for  adjusting  the  voltage  at  the  battery  to 
meet  changes  in  local  conditions  —  which  is  usually  very  desirable. 

Such  installations  are  very  satisfactory  and  economical,  showing 
a  saving  in  investment  over  copper  and  generating  machinery,  as 
well  as  a  considerable  saving  in  energy,  as  not  only  is  the  energy 
transmitted  at  its  average  current  value  to  such  a  point  on  the  line, 
but  the  average  current  consumption  is  lessened  by  the  increase  of 
voltage  at  the  point  of  consumption;  and  this  increase  and  main- 
tenance of  voltage  very  often  brings  about  an  actual  reduction  in 
wattage  at  the  point  of  consumption,  because  of  the  higher  accelera- 
tion rates  permitted  by  the  cars  themselves,  resulting,  as  is  well 
known,  in  a  considerable  reduction  in  energy  consumed  where  stop- 
ping and  starting  is  at  all  frequent.  A  booster  for  such  a  purpose 
is  usually  an  independently  excited  booster  located  at  the  power- 
house and  hand-controlled,  so  as  to  have  control  over  the  average 
output  over  the  battery  feeder. 

The  automatic  control  of  a  battery  by  its  booster  when  the  battery 
is  connected  in  parallel  with  generating  machinery  of  a  conptant  or 
rising  characteristic  is  accomplished  in  one  of  the  following  ways : 


ENTZ:     ELECTRIC  RAILWAY  STORAGE  BATTERIES.        281 

A  regulating  battery  is  generally  discharged  at  a  rate  at  least  as 
high  as  its  one-hour  rate ;  that  is  to  say,  the  rate  at  which  it  would 
discharge  continuously  without  its  voltage  drop  becoming  too  great. 
This  does  not  mean  that  a  battery  is  totally  discharged  at  this  rate 
in  one  hour's  time,  as  a  reduction  in  the  rate  would  permit  consid- 
erably greater  capacity  to  still  be  taken  out  of  the  battery  without 
its  voltage  falling  too  few.  Within  the  full  range  of  the  one-hour 
capacity  of  a  battery  the  voltage  change  for  a  change  of  the  one-hour 
rate  of  current  is  from  5  to  7  per  cent,  due  to  the  internal  ohmic 
resistance  of  the  battery,  and  this  change  of  voltage  is  simultaneous 
with  the  change  of  current.  If  the  full  rate  of  current  be  main- 
tained for  30  seconds,  an  increased  change  of  voltage  of  from  4  to  5 
per  cent  will  take  place  in  about  30  seconds'  time,  due  to  polariza- 
tion. After  30  seconds  the  increased  change  of  voltage  due  to  po- 
larization is  comparatively  slight,  except  at  the  very  end  of 
discharge  or  of  a  full  charge.  The  booster  must,  therefore,  be  pro- 
vided so  as  to  give  a  voltage  of  about  12  per  cent  of  the  battery  volt- 
age at  the  time  that  the  battery  is  charging  or  discharging  at  its 
maximum  rate;  and  we  must  further  insure  that  it  will  give  a 
voltage  of  20  per  cent  of  that  of  the  battery  at  a  rate  of  current  of 
from  one-third  to  one-fifth  that  of  the  maximum  rate,  in  order  to 
bring  the  battery  up  to  a  point  of  full  charge.  The  characteristic 
of  most  boosters  allows  them  to  give  this  additional  voltage  at  re- 
duced current  with  but  comparatively  little  increase  in  the  size  of 
their  field  magnets. 

The  automatic  excitation  of  the  booster  field  is  accomplished 
either  by  including  an  exciting  coil  in  the  working  circuit  by  means 
of  which  the  full  output  of  the  station  to  be  regulated  passes 
through  this  coil,  so  that  an  increased  load  demand  strengthens  the 
booster  field  and  gives  added  voltage  to  the  battery  circuit  sufficient 
to  cause  it  to  discharge  by  an  amount  equal  to  the  increase,  thus 
keeping  the  load  on  the  generator  constant,  or  to  take  any  propor- 
tion of  the  increased  load  that  is  desirable.  Such  a  main  exciting 
coil  in  the  working  circuit  must  be  neutralized  by  a  separate  excit- 
ing coil,  so  that  with  any  predetermined  average  output  of  the 
station  the  booster  shall  neither  add  nor  oppose  its  voltage  to  that  of 
the  battery.  For  currents  below  this  established  load,  this  opposing 
coil  becomes  stronger  and  reverses  the  polarity  of  the  booster,  caus- 
ing the  battery  to  charge  by  the  proper  amount  to  maintain  the 
regulation  desired.  In  order  to  make  such  a  combination  as  stable 
as  possible,  another  main-current  coil  has  been  included  in  the  gener- 


28i>        ENTZ:     ELECTRIC  RAILWAY  STORAGE  BATTERIES. 

ator  circuit,  so  that  an  increase  of  current  falling  upon  the  gener- 
ator following  an  increase  of  outside  load  would  further  affect  the 
battery  and  cause  it  to  discharge.  Where  the  outside  main-current 
coil  has  been  adjusted  to  exactly  meet  the  state  of  the  battery  and 
so  effect  absolutely  constant  current  delivered  from  the  generator, 
this  inside  coil  in  the  generator  circuit,  of  course,  accomplishes  no 
purpose ;  but  it  prevents  any  lack  of  exact  adjustment  affecting  the 
regulation  to  any  great  degree,  and  where  very  perfect  regulation 
is  required,  this  form  of  booster  is  very  extensively  used  and  is  gen- 
erally known  as  a  differential  booster. 

Eegulating  altogether  by  variations  in  the  generator  load  while 
trying  Jx>  keep  that  variation  within  small  limits,  calls  for  some 
means  of  magnifying  the  effect  of  such  variations  upon  the  booster 
excitation.  There  are  two  methods  of  this  kind  in  general  use,  in 
one  of  which  a  small  generator  with  a  voltage  normally  equal  to  that 
of  the  station  bus  has  included  in  its  circuit  the  exciting  coil  of 
the  battery  booster.  When  the  voltage  of  the  small  generator  and 
that  of  the  bus  are  equal,  no  current  flows  through  this  booster  ex- 
citing coil.  This  small  generator  is  known  as  a  counter  e.m.f.  gen- 
erator, and  derives  its  field  excitation,  and,  consequently,  its  voltage, 
from  a  coil  placed  in  the  generator  circuit,  the  said  coil  being  so 
adjusted  that  the  average  load  that  is  to  be  kept  upon  the  generator 
produces  a  voltage  of  the  counter  e.m.f.  generator  equal  to  and  op- 
posed to  that  of  the  station  voltage,  so  that  under  such  conditions 
the  battery  is  neither  charging  nor  discharging.  If,  now,  the  gener- 
ator output  increased  10  per  cent,  the  voltage  of  the  counter  e.m.f. 
generator,  if  it  has  a  perfectly  straight  characteristic,  will  increase 
10  per  cent  above  the  station  voltage,  and  this  excess  of  voltage 
should  be  sufficient  to  excite  the  booster  to  an  extent  necessary  to 
cause  the  battery  to  discharge  the  balance  of  the  load  increase  which 
caused  the  increase  upon  the  generator,  part  having  fallen  upon  the 
generator  for  the  purpose  of  effecting  the  regulation.  The  lowering 
of  the  generator  output  following  the  lowering  of  the  station  out- 
put acts  in  the  same  manner,  sends  a  reverse  current  through  the 
booster  field  and  causes  the  battery  to  charge. 

If,  as  cited  above,  regulation  of  the  generator  load  within  10 
I  er  cent  were  to  be  maintained,  the  output  of  the  counter  e.m.f. 
generator  would  have  to  be  10  times  that  of  the  energy  required  for 
the  field  excitation  of  the  booster,  as  but  10  per  cent  of  its  voltage 
is  applied  for  that  purpose.  If  the  regulation  were  to  be  5  per  cent 
in  either  direction,  the  output  of  the  counter  e.m.f.  generator 


ENTZ:     ELECTRIC  RAILWAY  STORAGE  BATTERIES.        283 

would  have  to  be  20  times  that  of  the  energy  required  for  the  booster 
field  excitation.  The  excess  output  is,  of  course,  not  lost,  but  passes 
to  the  line.  The  maintenance  of  any  fixed  load  upon  the  generators 
in  this  system  is  controlled  by  means  of  variable  shunts  around  the 
exciting  coil  of  the  counter  e.m.f.  generator,  which  carries  all  the 
generator  output. 

The  other  method  of  regulating  by  variations  in  the  generator 
load  is  by  means  of  an  electromechanical  regulator.  This  regulator 
consists  of  two  or  more  groups  of  carbon  discs,  connected  in  the 
manner  of  the  Wheatstone  bridge,  with  the  exciting  field  coil  of  the 
booster  connected  in  the  position  of  the  galvanometer.  A  pivoted 
lever  is  so  mounted  that  its  movement  brings  pressure  to  bear  upon 
one  set  of  the  groups  and  releases  it  upon  the  other,  so  as  to  change 
their  respective  resistance  and  to  vary  and  reverse  current  through 
the  field  of  the  exciting  coil.  To  one  end  of  the  lever  an  adjustable 
spring  is  attached  and  to  the  other  end  a  magnet  core  influenced  by 
the  current  in  the  generator  circuit.  At  the  average  generator  load 
which  is  to  be  maintained,  the  pull  of  the  magnet  is  balanced  by 
the  pull  of  the  spring  at  the  other  end  of  the  lever.  Under  these 
conditions  the  pressure  upon  the  two  groups  of  carbons  is  the  same, 
and  no  current  flows  through  the  booster  field  coil.  A  slight  in- 
crease of  current  in  the  generator  circuit  is  sufficient  to  cause  addi- 
tional pressure  upon  one  of  the  groups  of  carbons  compared  with 
the  other,  and  send  current  to  the  field  regulating  coil  of  the  booster 
in  a  direction  to  cause  the  battery  to  discharge,  which  it  does  to  an 
amount  practically  equal  to  the  increase  of  load  in  the  outside  cir- 
cuit, letting  only  a  small  portion  of  the  additional  load  fall  upon 
the  generator  to  effect  the  regulation.  If  the  generator  load  is  de- 
creased following  the  decrease  in  the  outside  load,  the  spring  be- 
comes stronger  than  the  magnet,  and  a  pressure  is  put  upon  the 
opposite  group  of  carbons,  reversing  the  current  through  the  booster 
field  coils  and  causing  the  battery  to  charge. 

It  has  been  found  that  very  close  regulation  can  be  maintained  in 
this  way,  even  with  a  load  varying  almost  instantaneously.  Regula- 
tion of  less  than  2  per  cent  in  either  direction  has  been  frequently 
obtained.  Complete  control  of  the  output  of  the  generators  is 
-secured  by  this  system,  and  the  generators  can  be  set  to  run  at  any 
average  load  desired,  by  simply  varying  the  strength  of  the  spring 
•opposing  the  magnet.  If  the  pull  of  the  spring  is  increased,  the 
«ienerator  current  is  immediately  increased  to  a  corresponding  de- 
cree, as  otherwise  the  battery  would  charge  till  the  increase  of  the 


284        ENTZ:     ELECTRIC  RAILWAY  STORAGE  BATTERIES. 

generator  load  would  balance  the  spring  pull.  The  end  of  the 
spring  carries  a  pointer,  and  there  is  a  calibrated  scale  in  amperes 
by  which  the  generator  output  can  be  instantly  set  at  its  desired 
value. 

This  form  of  regulator  is  mounted  on  a  switchboard,  and  occupies 
not  much  more  space  than  the  ordinary  recording  wattmeter.  The 
spring  and  its  indicator,  as  well  as  the  carbons,  are  on  the  front  of 
the  board,  and  the  lever  extends  through  the  board,  and  in  stations 
of  any  considerable  size  carries  a  simple  horseshoe  of  soft  iron  which 
is  hung  over  the  bus-bar  carrying  the  total  load  of  the  generators. 
The  usual  connection  for  such  a  regulator  is  to  have,  electrically 
considered,  two  groups  of  carbons.  These  are  connected  all  in 
series,  and  by  means  of  a  connection  made  to  the  storage  battery  a 
small  current  is  maintained  through  them.  At  the  middle  point  of 
the  carbons,  which  is  the  point  where  pressure  is  divided,  a  lead  is 
taken  through  the  field  coil  of  the  booster  to  the  middle  point  of 
the  battery,  to  which  the  two  ends  of  the  carbons  are  connected.  In 
this  way,  when  the  pressure  on  the  two  groups  of  carbons  is  equal 
and  the  resistance  is,  therefore,  equal,  there  is  no  difference  of  po- 
tential between  the  midway  point  of  the  carbons  and  the  midway 
point  of  the  battery. 

In  plants  where  very  large  boosters  are  used  it  is  desirable  to 
magnify  the  effect  of  the  regulator  by  means  of  an  exciter  con- 
nected between  the  regulator  and  the  booster,  rather  than  to  increase 
the  size  of  the  regulator.  This  regulator  has  some  advantages  over 
any  other  method  of  battery  regulation,  in  that  it  is  possible  to  ad- 
just the  sensitiveness  of  regulation  on  the  charge  side  of  the  battery 
as  compared  with  the  discharge,  and  vice  versa.  For  instance,  in  a 
generating  station  or  a  sub-station  with  a  fluctuating  load,  it  is  not 
necessary  or  always  desirable  to  maintain  the  load  on  the  generating 
machinery  absolutely  at  its  ratings  but  to  allow  it  to  share  the  in- 
creased loads  to  some  considerable  extent,  in  order  to  reduce  the 
discharge  rate  of  the  battery.  If  this  is  done  by  any  direct  means 
of  field-coil  regulation  it  will  follow  that  if  the  generating  apparatus 
shares  a  portion  of  the  overload  it  will  also  have  to  share  the  under- 
loads, or  loads  below  the  average,  in  the  same  proportion. 

With  the  carbon  regulator,  on  the  other  hand,  by  the  introduction 
of  a  resistance  in  one  of  the  groups  of  carbons,  the  regulation  on 
discharge,  for  instance,  may  be  made  of  any  degree  of  sensitiveness, 
so  as  to  allow  the  generator  machinery  to  share  any  portion  of  the 
overloads,  while  on  the  underloads  full  sensitiveness  of  regulation 


ENTZ:     ELECTRIC  RAILWAY  STORAGE   BATTERIES.        285 

may  be  maintained  and  the  load  on  the  generators  not  allowed  to 
drop  off  below  the  average.  In  this  way  the  battery  may  be  accu- 
mulating charge;  as  it  receives  more  charge  than  discharge,  the 
actual  variation  of  load  on  the  station  is  considerably  lessened  and 
the  maximum  output  of  the  generating  machinery  and  the  battery 
is  not  increased.  In  this  manner  the  overload  capacities  of  en- 
gines, generators,  rotary  converters,  etc.,  may  be  utilized  to  the 
fullest  advantage,  and  the  battery  may  be  discharging  at  very  high 
rates;  but  by  taking  full  advantage  of  every  dropping  off  of  the 
load  below  a  predetermined  point  sacrifice  as  little  of  its  capacity 
as  possible,  and  may  assist  the  generator  on  the  peak  of  the  load, 
while  losing  but  a  minimum  of  its  capacity.  Also  with  this  form 
of  regulator,  a  zone  of  non-regulation  may  be  created  extending  say 
from  10  per  cent  above  and  below  the  average  load,  whereas  for 
loads  above  and  below  this  the  regulation  may  be  as  perfect  as  pos- 
sible. This  permits  of  reducing  the  total  amount  of  charge  and 
discharge  in  ampere-hours  that  a  battery  may  receive  by  a  very 
great  amount,  while  keeping  the  variation  of  the  load  on  any  system 
within  non-objectionable  limits,  and  the  life  of  the  battery  may  be 
materially  increased,  often  without  reducing  any  of  its  benefits. 

As  to  the  construction  of  a  battery  for  railway  service,  it  is  pretty 
well  established  that  the  positive  plates  should  be  of  the  "  Plante  " 
type  and  not  of  the  "  pasted  "  type ;  while  the  negative  plates  are 
preferably  of  the  "  pasted  "  type. 

The  characteristic  trouble  of  negative  plates  has  been  loss  of  ca- 
pacity due  to  shrinkage  of  the  spongy,  finely  divided,  active  material 
into  a  denser  and  less  porous  material.  This  has  particularly  been 
true  of  "  Plante  "  negative  plates,  where  the  active  material  is  rela- 
tively small  in  quantity  and  has  been  reduced  from  the  peroxide 
previously  formed  from  the  plate  itself.  A  process  has  been  dis- 
covered of  manufacturing  a  negative  active  material  which  always 
retains  its  loose,  spongy,  porous  condition ;  but,  as  this  has  but  little 
mechanical  strength,  means  have  to  be  provided  in  the  plate  for 
retaining  it  in  position.  Such  plates  have  proven  eminently  satis- 
factory in  service  and  extended  tests  show  a  very  greatly  increased 
life  and  the  maintenance  of  low  resistance  and  low  polarization 
factors. 

In  considering  the  life  of  a  positive  "  Plante  "  plate,  it  should  be 
taken  into  account  that  the  life  in  ampere-hours  of  a  pound  of 
lead  entering  into  the  construction  of  a  positive  plate  is  not  gov- 
erned by  the  surface  development  of  the  lead,  but  by  the  means 


286       ENTZ:     ELECTRIC  RAILWAY  STORAGE  BATTERIES. 

which  have  been  provided  for  retaining  the  active  material  formed 
from  the  plate  itself  in  proper  contact  with  it,  and  the  prevention 
of  the  loss  of  such  active  material  from  being  washed  away  or  car- 
ried away  by  the  gases  which  rise  from  the  surface  of  the  plate. 
The  extended  development  of  a  pound  of  lead  increases  the  capacity 
which  it  would  yield  on  any  one  discharge,  but  lessens  the  total 
number  of  discharges  available  by  more  than  a  proportionate 
amount,  a  very  highly-developed  plate  yielding  less  total  life  in 
ampere-hours  mainly  because  its  mechanical  structure  and  its  con- 
ductivity are  affected  to  a  greater  extent  by  the  removal  or  loss  of 
a  portion  of  the  substance  of  the  plate.  For  this  reason  the  de- 
velopment of  the  active  lead  should  be  made  in  such  a  manner  that 
it  will  provide  secure  receptacles  for  the  retaining  of  the  active 
material;  and  the  necessary  further  corrosion  of  the  active  lead  for 
the  purpose  of  replacing  active  material  carried  away  should  not 
interfere  with  the  mechanical  strength  or  with  the  conductivity  of 
the  plate. 

No  modern  battery  installed  for  railway  service  should  be  in  dan- 
ger of  a  break-down  at  any  rate  of  discharge  that  could  possibly  be 
imposed  upon  it,  and  in  well-designed  batteries  there  is  absolutely 
no  danger  of  break-down  due  to  any  rate  of  overload. 

Some  years  ago  the  electrical  engineer  was  disposed  to  look  upon 
a  storage  battery  with  more  or  less  misgiving.  Even  at  the  present 
time  there  may  be  found  occasionally  an  engineer  who,  not  realiz- 
ing the  progress  that  has  been  made  in  this  art  and  the  place  that 
the  storage  battery  has  established  for  itself,  is  disposed  to  take  this 
skeptical  attitude.  If,  however,  the  history  of  the  storage  battery 
business  for  the  past  10  years,  which  period  practically  covers  its 
entire  commercial  history,  should  be  compared  with  the  first  10 
years  of  any  other  electrical  apparatus,  we  believe  that  the  com- 
parison will  show  a  series  of  complete  successes  and  the  absence  of 
anything  approaching  a  failure  or  setback,  that  will  compare  favor- 
ably with  the  history  of  any  other  electrical  apparatus. 

DISCUSSION. 

CHAIRMAN  DUNCAN:  The  paper  is  now  open  for  discussion.  I  would 
like  to  ask  Mr.  Sprague  if  the  New  York  Central  is  going  to  put  in  bat- 
teries, or  if  he  can  say  whether  they  are  or  not? 

Mr.  F.  J.  SPRAGUE:  That  is  a  question  I  cannot  answer  at  present. 
My  experience  with  storage  batteries  has  been  such  as  to  lead  me  to 
regard  them  with  favor  in  some  classes  of  work.  On  the  South  Side  Ele- 


ENTZ:     ELECTRIC  RAILWAY  STORAGE  BATTERIES.       287 

vated  road  in  Chicago,  storage  batteries  were  introduced  for  two  reasons, 
one  to  help  take  the  sharp  fluctuations  in  load,  and  the  other  to  provide 
additional  facilities  when  the  demands  of  the  road  were  growing  so 
rapidly  as  to  run  ahead  of  possible  direct  equipment.  No  boosters  were 
used,  the  batteries  responding  fairly  well  automatically  to  the  rise  and 
fall  of  potential  where  connected  to  the  line,  but  varied  somewhat  in 
action  by  cutting  in  or  out  an  extra  feeder. 

The  New  York  Central  presents  a  problem  which  is  materially  different 
from  that  of  elevated  and  suburban  roads.  Usually  on  those  classes  of 
service  there  are  a  large  number  of  units,  and  the  load  is  fairly  dis- 
tributed. The  New  York  Central  has  about  nine  sub-stations,  the  units 
weigh  from  150  to  700  tons,  and  the  sub-stations  are  a  considerable  dis- 
tance apart.  It  is  impossible  to  avoid  a  condition  which  is  emphasized 
on  heavy  steam  railway  work,  extreme  local  variations  of  load.  There  will 
probably  be  at  times  as  many  as  four  trains  supplied  almost  entirely  by 
one  sub-station,  while  at  other  times  there  will  not  be  any  load  whatever 
on  it.  Of  course  that  means  a  pretty  large  variation,  and  sometimes  a 
very  rapid  one. 

Personally,  I  am  strongly  in  favor  of  the  use  of  storage  batteries  in 
this  instance,  not  only  partly  to  relieve  the  sub-station  machinery  and 
to  reduce  its  capacity;  but  also  to  provide  a  reserve,  in  case  of  any  acci- 
dent to  the  central  power  plants  or  transmission  system. 

The  equipment  is  being  laid  out  with  the  idea  of  maintaining  train 
movements  from  two  stations,  either  of  which  in  emergency  can  operate 
the  entire  service  for  a  reasonable  time.  I  do  not  think  that  in  the 
matter  of  cost,  all  things  considered,  there  would  be  much  difference  be- 
tween the  installation  of  a  plant  with  or  without  storage  batteries,  that 
is,  the  saving  of  central  station  and  sub-stations  would  be  about  offset 
by  the  cost  of  batteries  and  boosters. 


ELECTROLYSIS  OF  UNDERGROUND 
CONDUCTORS. 


BY  PROF.  GEORGE  F.  SEVER,  Columbia  University. 


In  the  spring  of  1903,  Mr.  L.  B.  Stillwell,  Mr.  F.  N.  Water- 
man and  the  writer  felt  that  it  was  desirable  to  compile  and  co- 
ordinate as  much  information  as  could  be  procured  on  the  subject 
of  the  electrolysis  of  underground  conductors,  due  to  the  operation 
of  electric  railways.  It  was  felt  that  both  the  opinions  regard- 
ing electrolysis  and  the  practice  in  remedying  the  same  were  so 
diverse  that  it  would  be  of  value  to  collect  all  this  information 
and  present  it  before  the  International  Electrical  Congress. 
Through  the  efforts  of  the  first-named  gentlemen  the  practice  of 
the  electric  street  railways  was  secured,  and  all  the  world's  litera- 
ture, which  was  available,  was  collected  and  put  into  the  form  of 
a  digest.  The  writer  collected  information  regarding  the  atti- 
tude of  the  municipalities,  including  such  ordinances  regarding 
electrolysis  as  had  been  put  into  effect  up  to  that  time.  The  data 
was  put  into  tabular  form  by  Mr.  Waterman,  and  through  the 
courtesy  of  both  Mr.  Stillwell  and  Mr.  Waterman  the  writer  has 
been  able  to  present  the  final  results  before  this  Congress. 

The  data  is  presented  in  the  five  tables  which  are  attached  hereto. 

Table  I  shows  the  street  railway  practice  in  the  United  States 
regarding  the  use  of  return  feeders  and  the  effect  of  increasing 
the  capacity  of  these  feeders.  The  reports  are  shown  from  102 
electric  railways. 

Table  II  shows  the  recommendations  which  have  been  made  to 
29  municipalities  by  city  and  other  engineers.  The  results  of 
these  recommendations  are  shown  in  a  few  cases. 

Table  III  shows  the  most  essential  electrical  features  of  the 
municipal  ordinances  which  are  in  force  in  12  different  munici- 
palities. The  inconsistencies  in  some  of  these  ordinances  are 
remarkable,  particularly  in  the  cases  of  Atlantic  City  and  Altoona. 

[288J 


SEVER:     UNDERGROUND  CONDUCTORS.  289 

Table  IV  presents  a  summary  of  the  opinions  of  municipal  offi- 
cers as  extracted  from  the  letters  received  from  them.  Fifty 
municipalities,  widely  distributed,  were  heard  from. 

Table  V  presents  a  summary  of  expert  opinion  concerning  elec- 
trolysis. This  expert  opinion  shows  many  differences  in  the  recom- 
mendations as  to  remedy.  It  is  the  writer's  hope  that  the  discussion 
on  this  presentation  may  be  full  and  that  some  definite  conclusions 
may  be  arrived  at  for  the  betterment  of  the  conditions  which  are 
known  to  exist  in  some  localities. 

ELEC.  RYS. 19. 


200 


SEVER:  UNDERGROUND  CONDUCTORS. 


TAB 

SUMMARY  OF  STKF-ET  RAILWAY 


1 

E: 
X 

1 
1 

a 

4 
5 

6 

7 

8 
9 

10 

11 
12 
13 

14 
15 

16 
17 

18 

19 
20 

21 

22 
28 

1 

03 

City. 

| 

1 
| 

(2 

Name   of    electric 
street  railway 
company. 

System  of  operation. 

Date  of  electrical  in- 
stallation. 

Miles  of  track. 

Weight  of  rails. 

Bonding 
system  . 

Number  and  size  of  1 
bond  per  joint. 

Nature  of  re- 
turn feeder 
system. 

Ala... 

Ala... 
Conn. 
Conn. 
KJonn. 

Fla.. 
Ga... 

Ga... 
111.  .  .  . 

111.... 

111.... 
111.... 

m.... 

Ind.. 
Ind.. 

Ind.. 
Iowa. 

Ky... 

Me... 
Me... 

Me... 

Md... 
Md... 

Birmingham  
Huntsville 

88,400 

8,100 
9,600 
9,600 
2,400 

28,500 
10,200 

12,000 
22,500 

1,700,000 

25,000 
18,800 
15,100 

7,800 
10,500 

18,100 
15,000 

20J,000 

22,000 
8,000 

8,100 

17,100 
18,600 

Birmingham    R  y  . 
Lt  &  Pw  Co  

1894 

1900 
1895 

99 

8 
10 
13 

18 

7 

27 
12 
184 
14 

5 

4 

7 

18 

8 
142 

27 

7 

2 
7 
14 

60- 

88 

60 
56- 
80 

60 

60 

45- 

70 
40- 
60 

70 

60- 
75 

95 

60- 

70 

50 
40- 
60 

56 

30- 

86 

60 

56 
60- 
100 

56 

48- 
56 

60 

40- 
73 
56- 
72 

W.&M.. 
Copper  .  . 

Copper.. 
Copper  .  . 

Copper  .  . 

Chase  S.. 
Protect.. 

All  wire. 

4-0 

4-0 
2-0 

2 
4-0 

1-0 
2-0 

2 
2-0 

2 
4-0 

2-0 
4-0 
4-0 
2-0 

4 

4-0 
1-0 

2-0 
4-0 

None  

Huntsville  Ry.  Lt. 
&  Pw  Co  

None  

None 

Bristol  

B.  &  P   Ry.  Co.... 

Middletown  
Montville  .  . 

M.  St.  Ry.  Co  
M  St  Ry  Co  



No.   2    track 
wire 

None  

Jacksonville  .... 
Athens  

Dahlonga  .  . 

1  ret.  feeder. 
None  

A.  Elec.  Ry.  Co  — 
G.  &  D.  Elec.  Ry. 



1895 

None  

Alton  

Chicago 

A.  Ry.  Gas  &  Elec. 

On  all  lines.  . 
On  all  main 
lines  

Cast  weld 

Copper  .. 
Wire  .... 
Protect.  . 
Wire  

Wire  
A.S.&W. 
Wire  .... 
A.S.&W. 

Chase  S. 
protect. 

Chic  ago 
protect. 

Brown 
crown  .  . 

CJDI  er 

• 

None  

F.  Ry.  Lt.  &  Pw. 
Co 

Ret.  feed.... 
None  
None.. 

Jacksonville  .... 

Columbus  

J.  S.  Cramp's  Elec. 

None  

LaFayette  .. 
Keokuk  

L  F  St  Ry   Co... 

On  one  line.. 
None 

K.    Elec.     Ry.    & 

Louisville  
Bangor  ......... 

L.  Ry.  Co  

Penobscot  Central 

M  to  2  miles 
from  P.  S.. 

None  
Ret.  feeds... 

None  
No.2gr.wlre 

None  

Calais  

Kennebunkport.  . 

Cumberland*  .  .  •  • 
Hagerstown  

Atlantic    Shore 
Line  Ry  

H  Rv  Co... 

Copper  .  . 

2-0 

4-0 

8L'\'1-:R: 


CONDUCTORS. 


201 


LE  I. 

PRACTICE  IN  THE  UNITED  STATES. 


.S 

2 

| 

8 

a 

6 

I 
i1 

m 

1 

Q. 

S* 

1- 

a, 

1 

of  power  statioi 

:imum  curre 
from  each. 

imumlinevolta 

Nature 
of  soU. 

Nature 
of  corro- 
sion. 

Extent 
of  corro- 
sion. 

Any  claim 
against 
railway 
company? 

What  remedy 
applied? 

Effect  of 
remedy. 

p 

E 

3       -S 

£ 

X 

S      .2 

N'o... 

No... 

None  . 

1 

350 

Some.  ... 

No.  

None  

No 

No 

None 

1 

300  475  Fav     .  . 

No  

No 

No 

None 

1 

500600  

No  

No 

Yes.. 

1 

500450 

No  

No... 

No... 

None  . 

1 

2,500350 

Some  

Yes  

Larger  bonds.  . 

No    more 

trouble. 

No 

No... 

None  . 

1 

700375 

None  .... 

No  

No 

No  .. 

None  . 

1 

400 

450 

Unfav.. 

No  

No 

No 

None  . 

1 

500 

4OI 

No  

No... 

No... 

None  . 

i 

1,200 

450 

None  .... 

No  

No... 

Yes.. 

4 

12,000400 

Some.  ... 

Nothing 

definite.  . 

None  

No     . 

No... 

None  . 

1 

8,600 

450 

Fav.... 

Some  .  .  . 

No  

None  

No 

No... 

None  . 

1 

400425 

No 

None           •  .  • 

No... 

No... 

None  . 

I 

'450 





None  .... 

Once  

Analysis 
showed  rust. 

Yes 

Yes.. 

1 

250480 

None  

No  

No... 

No... 

None  . 

1. 

500 

Unfav.. 

None.... 

Once  

Proved     earth 

No 

No... 

None  '. 

1 

500450 

None  

No  

No  .. 

No... 

None  . 

1 

500450 

None  .... 

No  

Yes.. 

Yes.. 

1 

10,000 

500 

Some  .... 

Yes  

Ret.  feeds.  .... 

Less    com- 

plaint. 

Mo... 

No... 

None  . 

2 



480 





None.... 

No  





Tee.. 

Yes.. 

1 

850 

450 

Some  .... 

Yes  

Improving    re- 

Less  trou- 

ble. 

N.»... 

No... 

None. 

3 

1,000 

360 

None  .  .  , 

No  

) 

No... 

No  

No... 

No... 

None. 

1 

800 

350 

Fav.  at 

point 

At    one 

point  .. 

No  

None  



21)2 


SEVER:  UNDERGROUND  CONDUCTORS. 


TABLE  I  — 


Number.  | 

1 

City. 

Population  served. 

Name    of  electric 
street  railway 
company. 

d 

.0 

Date  of  electrical  in- 
stallation. 

Miles  of  track. 

Weight  of  rails. 

Bonding 
system. 

Number  and  size  of 
bond  per  joint. 

Nature  of  re- 
turn feeder 
system. 

24 
25 

20 

27 

28 

29 

30 

31 
32 
83 

84 

85 

36 
87 

38 

89 

40 
41 

42 
48 

44 

45 

46 

47 

48 
49 

Mass. 
Mass. 

Mass. 

Mass. 
Mass. 

Mass. 

Mass. 

Mass. 
Mass. 
Mass. 

Mass. 

Mich. 

N.  H. 

N.  J. 

N.  J. 

N.  J. 

N.  J. 

N.Y. 

N.Y. 

N.Y. 

N.Y. 
N.Y. 

N.Y. 

N.Y. 

N.Y. 

N.Y. 

Amherst  
Athol  

5,000 
7,100 

A.  &  S.  St.  Ry.  Co. 
A.  &O.  St.  Ry  

C.  C.  &  E.  Traction 
Co  

:::::: 

'.'.'.'. 

15 

7 

5 
B 

32 

16 
23 

60 

50- 
90 

50 

60 
70- 
90 

45- 
60 

48- 
60 

Copper.. 

S.V'.'&B. 
Crown.  .  . 

4-0 

4-0 

1-0 
2-0 

4-0 

4-0 
4-0 
2 
4-0 

2-0 

2 

4-0 

Fewgr.  wires 
Ret.  feed.... 

Gr.  wire  
None  

On  all  lines.  . 
None  

1,600 
12,400 

10,000 

8,000 

45,700 
45,700 
658,000 

8,100 

9,500 

2,500 
4,000 

76,000 

8.100 
10,600 

C.  Elec.  St.  Ry.  Co. 
F.  &  L.  St.  Ry.  Co. 

G.W.&F.St.R.R. 
Co  

Fitchburg  ...... 

Gardner  ........ 

Greenfield  ...... 

fG.D.&N.St.Ry. 
1     Co  

Holyoke  

1  G.  &  T.  F.  St.  Ry. 

[     Co 

I 

None  

Holyoke  
Lowell 

H  St  Ry  Co 

Crown... 

On  one  line.  . 

On  nearly  El- 
lines  

None  .  

None  
Some  

2-0  for  each 
track  

B.  &  N.  U.  Ry.  Co. 

C.  M.  &  H.  St.  Ry. 
Co  

440 

18 

8 
8 
24 

67 

6 

12 
42 
37 

8 
6 

27 

7 
4 

19 
5 

90 

60- 
90 
45- 
60 

48 

60- 
70 

70- 
90 

65- 
70 

60 

80 

40 
56- 
90 

50- 
90 

56 

48- 
60 

56- 

80 
56 

Crown... 

Escanaba  

Chester  
Asbury  Park.... 

Camden  
KevDort 

E.  Elec.  St.  Ry.  Co. 

C.  &  D.  Ry.  Ass'n.. 
A.  C.  Elec.  R.  R. 
Co  



.... 

C.  &  Sub.  Ry.  Co. 

J.  C.  Traction  Co. 
M  Traction  Co 



.... 

None  

Millville     .. 

M.  &  E.. 

Copper  .  . 
Crown... 

M.  &  E.. 

Chicago 
plastic 
wire  .  . 

4-0 

4-0 

2 

4-0 

None  
None  

Albany 

A.  &  H.  R.  R.  Co  -j 

B.Ry.  Co  
Ont.   Lt.  &  Trac. 
Co 

Third 
rail. 

E: 

Binghamton  
Canandaigua  .... 

Corning  
El  mi  ra  .......... 

60,000 
6,000 

12,500 
85,700 

8,700 

18,500 

18.000 
12,000 

Ret.  feed.... 
Ret.  feed.... 
None  

C.  &P.  P.St.Ry.. 

E.  Wat.  Lt.  &  R.  R. 
Co  

•  

.... 

Ret.  feed.... 
Ret.  feeds... 

Fishkill  

Citizen  R.  R.  Lt.  & 

Fredonia  

Gloversville  
Hornel  Lsville  .  .  . 

D.  &F.R.  R.  Co.. 
F.  J.  &  G.  R.  R... 



.... 

M.  &  E. 
O.B.Co. 

Copper  .  . 
Copper  .  . 

4-0 

2-0 
4-0 

Ret.  feed.... 

SEVER:  UNDERGROUND  CONDUCTORS. 


(Continued). 


2 

2 

s 

s 

43 

o 

6 

0 

<D 

o3 

p 

t 

r 

rea  is  draii 

power  stati 

£-.     . 
O  §j 
§P 

! 

Nature 
of  soil. 

Nature 
of  corro- 
sion. 

Extent 
of  corro- 
sion. 

Any  claim 
against 
railway 
company? 

What  remedy 
applied? 

Effect  of 
remedy. 

V 

•3, 

tS       o 

g 

f 

e 

f?       o 

I 

c 

F      fc 

fl 

i 

No...  No... 

None. 

9 

coo 

400 

None  No  

No...  Yes.. 

1 

606 





None....  No  





No.  .  .  No... 

None  . 

1 

'50 

None  ....  No... 

No       No      jNone  .    2 

200 

None  ttrt-      - 

No   .  .  Kn.       Nonp.  . 

1 

1  700 

450  

None  .... 

No  

No... 

Wet 

places 

1 



Sand, 

lime. 

clay 

No  

Area. 

No... 

\ 

•NV» 

No.  ..  No...  None  . 

1 

500390 

No...  Yea.. 

1 

750375 

Yes.. 

1 

8,500400 

Some  

Yes  

Gr.  wires  

Reduced   P. 

D. 

No... 

1 

100 

No  

No... 

No... 

None. 

1 

550 

None  .... 

No... 

No...  Yes.. 

No... 

No... 

None. 

2 

1,600 

575 



.......... 

None  .... 

No  



-f 

Area   No... 

None. 

4 



460 





Little.... 

Yes  

Investigation.. 

No    more 
trouble. 

No.  .  .  No... 

None. 

•8 

500 

1,000 

-100 

None  ....  No  

No...  No...  None  . 

1 





None  ....  No  





No.  .  .  No...  None  . 

3 

-100 

Clay... 

None         No 

No...  No...  Nona  • 

9 

1r>0 

None  .  .  .  No  I         

No... 

Yes.. 

1 

150 

too 

None  No  

No... 

No... 

None. 

1 

850 

175 

Fav.  ... 

None  ....  No  

No... 

No... 

None. 

1 

On  rails 

Yes  

Ret  feed  

Economy 

Ho... 

Yes.. 

1 

Some.... 

I  n  d  e  fl  - 

nitely.  .  . 

He... 

No... 

None. 

1 

800 

500 

Clay, 

gravel. 



Some  No  

Better  bonding 

Suppressed. 

No... 

,{ 

400  Fav 

•NTrmo 

No... 





1 



470  i.. 



None  None  !  



294 


SEVER:     UNDERGROUND  CONDUCTORS. 


TABLE  I— 


1 

£ 
~50 

51 
52 

53 
54 

55 
56 

57 

58 

59 
60 

61 
63 

63 

64 
65 

66 
67 

68 
69 
70 
71 

72 
73 

74 

1 

City. 

Population  served. 

Name  of    electric 
street  railway 
company. 

1 

OQ 

Date  of  electrical  in- 
stallation. 

Miles  of  track. 

Weight  of  rails. 

Bonding 
system. 

•s 

i 
n 

frnTS 
£§ 

E-° 

Nature  of  re- 
turn feeder 
system. 

N.Y. 

N.Y. 
N.Y. 

N.Y. 
N.Y. 

N.Y. 

N.Y. 

Ohio. 
Ohio. 

Ohio. 
Ohio. 

Ohio. 
Ohio. 

Ohio. 

Ohio. 
Ohio. 

Ohio. 
Pa... 

Pa... 
Pa... 
Pa  .. 

Hoosick 

30,000 

3,000 
13,000 

28,000 
7,500 

10,500 
114,000 

15,500 
1,400,000 

882,000 
126,000 

8,800 
125,000 

22,000 

22,000 
16,500 

12,000 
1,600 

9,600 
53,000 

Ben.  H.  Valley  Ry. 

17 

8 

8 

21 
17 

18 
88 

6 

42 
^ 

60 

56 
45- 
60 

45- 

80 

80- 
100 

45- 
73 

80- 
90 

50 
70 

Plastic 
wire  

Wire.... 

1-fl 

2 

1-0 

2-0 
3-0 

2 

800- 
000 

2-0 

2 
250- 
000 

2-0 

None  
None  

None  

Huntington  
Ithaca  

Jamestown  . 

H.  R.  R.  Co  
I.  St.  Ry.  Co  

J.  St.  Ry.  Co  



.... 

No.  2  to  No.  0 
gr.  wire... 

None  

Port  Chester.  .  .  . 

Seneca  Falls  
Utica  

N.  Y.  &  S.  Ry.  Co. 

G.  W.,S.  F.,&C. 
L.  Tr.  Co  



.... 

O.B.Co. 
Wire.... 

1-0  ret.  feed. 

U.  &  Mo.  Val.  Ry. 

Chillicothe  

C.  Elec.  St.  Ry.  & 
Pw.  Co  

Wire  .... 
Protect.. 

None  

C.  L.  &  A.  Elec. 
St.Ry.  Co  

Cleveland  

East  O.  Tr.  Co.... 

Columbus  

Dennison  
Toledo  

C.  L.  &S.Ry.  Co. 

50 
2 
60 
12 
47 
12 

5 

70- 
90 
48 

60 

60- 
70 

60- 
72 
56- 
82 

60 

70- 
80 

65 
80 

70 
60- 
90 

56 

m. 

90 
90 

w!?r- 

.... 

None  

U.  Elec.  Co  
T.  B.  G.  &  So.  Tr. 
Co  



.... 

Copper.. 

Crown.,. 
Crown... 
Copper.. 
Plastic 

4-0 

4-0 
4-0 

2 

4-0 

None  

Ret.  feed  .... 
None  

None  .  .  . 

L.  Elec.  Ry.  &Lt. 

Lima.  

East  Liverpool.. 

Marion  

W.  0.  Ry.Co  
U.  Pw.Co  

M.  St.  Ry.Co  

C.  E.  &  I.  St.  Ry. 
Co  



.... 

Gr.    wire    at 
sw  

M.  &B.. 

8-0 
4-0 

4-0 

2 
4-0 

4-0 
44) 

None  
None  .  . 

Carlisle  

0.  &  Mt.  H.  Ry. 
Co     . 

6 
81 

19 

49 

20 
92 

24 

Erie  ;.. 

E.  Elec.  Motor  Co. 

Media,Middlatown, 
A.  &  C.  El.  Ry.. 



Copper.. 
Copper  .  . 

Pa... 

Pa... 
Pa... 

Pa... 

Harrisburg  

Hazleton  
Lancaster  

Lebanon  .. 

60,000 

14,000 
41,000 

18,000 

L.  Tr.Co  
C.  Tr.  Co  

L.  V.  St.  Ry... 



.... 

Plastic 
wire... 

Copper.. 

4-0  ret.  feed. 
None  
None... 

SEVER:     UNDERGROUND  CONDUCTORS. 


2<J. 


( Continued). 


3 

3 

s 

d 

ft 

& 

1 

I 

1 

.2 

9 

t-,    • 

% 

*- 

P 

f 

i 

of  power  st 

ffl 
|| 

limum  line  \ 

Nature 
of  soil. 

Nature 
of  corro- 
sion. 

Extent 
of  corro- 
sion. 

Any  claim 
against 
railway 
company? 

What  remedy 
applied? 

Effect  of 
remedy. 

I 

3 

1 

6 

1 

No... 

No... 

None. 

1 

sno 

None  — 

Yes  

None  

No... 

|450  

i 

No... 

No...  None  . 

1 

1,000850 

One  case  . 

No  

Renewed 

Yes.. 

Yes.. 

2,000 

f>00 

Yes  

Area. 

1 

4frf) 

Fav.... 

No  

No... 

No... 

None  . 

1 



375 



None  .... 

No  





No... 

Yes.. 

5 

300 

None  .... 

No  

riOO 

None  .... 

No  

No... 

1 

10,000 

.10(1 

None  .... 

No... 

No  

No... 

No... 

None. 

9 

4-(0 

^one  ...; 

No  

No... 

1 

800500 

tf  one  

No... 

No... 

None  . 

4 

800400 

None  .... 

No  

No... 

Yes.. 



1 

1,200 

275 





None  .... 

No  





No 

No 

None  . 

_ 

900 

5BB 

No  

No... 

Yes.. 

2 

1,000 





Some  .... 

No  



No  . 

No 

None 

- 

500 

^00 

No  

No. 

No 

None 

400 

VAS... 

No  

No... 

MOI- 

No  

No... 

Yes.. 



1 

2,000 

400 

In  some 

Alleged 

Yes  

No  

Yes.. 

No... 

None. 

2 

1,800 

390 





Some  .... 

No  

Repaired 
bonds  .  . 

No    more 

trouble 

No... 

No... 

None  . 

2 

500850 

Fav.... 



None.... 

No  





No... 
No... 

No...  None  . 
No...  None  . 

1 
1 

1,800400 
5,500... 





Noth  i  n  g 
serious  .  . 
None....  No  



296 


BEYER:  UNDERGROUND  CONDUCTORS. 


TABLE  I 


I 

3 
fc 

75 

76 

77 

78 
79 

80 
81 

82 

83 

84 

S.5 

80 
87 

88 

j 
89 
90 

91 

92 

93 

«J4 

1 

City. 

Population  served. 

Name  of    electric 
street  railway 
company. 

1 
* 

>> 

CO 

Date  of  electrical  in- 
stallation. 

S 

Weight  of  rails. 

Bonding 
system. 

I" 

I 

§| 
|| 

fc 

Nature  of  re- 
turn feeder 
system. 

Pa... 

Pa... 
Pa... 

Pa... 
Pa... 

Tenn. 
Tenn. 
Tenn. 

Tenn. 

Vt.... 
Vt.... 

Va... 
Va... 
Va... 

W.Va 
Wis.. 

Wis.. 

Wis..1 
DL.J 

Mass. 

Lewistown  

McKeesport  
Philadelphia  .. 

4,500 
81,000 

L.  &  R.  Elec.  Ry. 

6 
85 

60- 
70 

70- 
90 
60- 
90 

40- 
80 

f>0- 
70 

35- 

60 
(50 

15- 

75 

60 
60 
50- 
(50 

8-0 
4-0 

4-0 
4-0 

8 

4-0 

1-0 
4-0 

None  

P.  McK.  &  C.  Ry. 
Co  

A.S.&W. 
Protect.  . 

Many.... 

4-0  ret.  feed. 
None  

Scranton  ....... 

103,000 

S.  Ry.  Co  

77 
50 

T 
16 

41 

8 
5 

9 

4 

Ret.  feed.... 

Ret.  feed... 

Ret.  feed.... 
None  

Philadelphia   . 

Bristol  

5,000 
•  82,500 
82,500 

14,500 

19,000 
3,500 

10,000 
16,500 
28,000 

80,uOO 
17,500 

18,500 

10,3UO 
17,000 

B.  B  L.  Ry  Co.... 

Copper.. 

Chatanooga  
Chatanooga  

R.  T.  Co.  of  C... 

C.  E.  Ry.  Co  

J.  &  Sub.  St.  R.  R. 
Co  



.... 

Copper, 

V£  mile  from 
P.  S    ... 

Ret.  feed.... 
Gr.  wires.  .  .  . 

None  

Turlington  
Springfield  ...... 

M.  P.  St.  Ry  Co... 

Chicago  . 
Crown... 

.... 

S  Elec  Ry  Co... 

Charlottsville.... 

C.  C.  &  Sub.  Ry.Co. 

6 

16 

20 
22 

2 

11 

90 

45- 
100 

60 
45- 
70 

: 

°?0 

54- 
94 

Protect.. 

Crown, 
G.  E... 
Protect.  . 

A.S.&W. 

Crown, 
G.  E... 

None.... 
AS  &W. 

4-0 

4-0 

4-0 
4-0 

None  

Ret,  feed.... 
None  

jvnchburer 

L.  Tr.  &  Lt.  Co.,  R. 
Ry.  &  Elec.  Co  .  . 

Parkersburg  .... 
Eau  Claire  7  

P.  M.&I.  Ry.Co.. 

C.  V.  Elec.  Ry.  Co. 

M.  AN.  Tr.  Co.... 
M.Ry.&Lt.Co.-j 

Manitowac  
MerriU  

D'ble 
trol. 

h 

None  

Metallic  

Boston      Elevated 

Protect, 
steel 
plug  .  . 

1 

4-0 
2 
4-0 
8 
4-0 

Ret.  feeds  on 
a    heaw 
traffic  line. 

SEVER:  UNDERGROUND  CONDUCTORS. 


297 


( Continued). 


3 

K 

3 

a 

2 

o 

£ 

0) 

S3 
O 

1 

6 

Maximum  current 
from  each. 

Minimum  line  voltage.  | 

Nature 
of  soil. 

Nature 
of  corro- 
sion. 

Extent 
of  corro- 
sion. 

Any  claim 
against 
railway 
company  ? 

What  remedy 
applied  ? 

Effect  of 
remedy. 

No... 
No... 

No... 

None  . 

1 
2 

600 
1,200 

375 

450 

No  

Fav.  ... 

None  .... 

No  

Yes  

Rebond       ret. 
feed  

No    more 
trouble. 

No    more 
trouble. 

1  -8  volt  P.  D. 

4- 
Pipes 

No... 

No... 
Yes.. 

No... 

Yes.. 

No... 

Yes.. 
Yes.. 

No... 

None  . 
None. 

2 

1 
1 

2 

2,100 

'i',m 

1,100 

350 

550 

4SO 

400 

450 
450 

** 



Some  

At      two 
places. 

None.... 
Some  ... 

None  .... 

No  
Yes  

Taps  to   pipes 
bonding  

Rebond  4-0  C. 

s  

No  
No  

No  
No  

Repaired  poor 
bonds 



Yes.. 
No... 

Yes 

400 

No  

On  rails.  . 

Nr>n« 

No  

River  plates  .  .  . 

I  m  p  ro  v  e  d 
power  . 

No  

N.... 

No... 

None. 

450 
1,600 

500 
000 

No  

NY»n«  .  . 

No... 

No... 
No... 

No 

Yes.. 
No... 

+ 
None  . 

2 
2 

1 

1 

1 
8 

600 
350 

500 

80 

8,800 

450 
450 

350 
500 

550 
400 

'TJVniA  .      .  No  

None  

Yes  
No  

Doubled  bond  . 

No    more 
claims. 

No  

Pipes 

He... 

No... 
No... 

None. 
None. 

Far.... 

Graphitic 

None  .... 
Some  ... 

No  
Yes  

Heavier  return 

Reduced 
danger 
1     areas. 

298 


SEVER:     UNDERGROUND  CONDUCTORS. 


TABLE  I- 


J 

a 

3 

i 

1 

|| 

03 

|| 

City. 

a 
o  • 

Name   of    electric 
street  railway 
company. 

1 

o 

Bonding 
system. 

Is, 

Nature  of  re 
turn  feeder 
system  . 

h 

*ri 

q_l  +2  1  OJ 

t->d 

J 

• 

s 

o  ^ 

O 

^ 

5 

1 

Pi 

I 

1 

1 

•3 

I"5 

£ 

02 

CH 

02 

M 

« 

K* 

fc 

95  TVTnca 

Middleboro 

6  900  Mid    W    #  R    R  St. 

Ry  Co 

BO 

70 

2 

4-0 

500,000  C.  M. 

ret  

% 

N    J. 

Pub  .  Serv  Corp  of 

70 

107 

Cast  pro- 
tect .  -.  . 

4-0 

Ret.  feed.... 

97N  Y 

Buffalo  

International    Ry 

Co 

98 

Ohio 

125  500 

C  Ry  &  Lt  Co 

1%  ^n 

M 

C.  B.  L.  &  N.  Tr. 

107 

Copper  .  . 

.... 

Ret.  feed.... 

Co  

70 

4-0 

None 

100 

S.  C. 

Columbia  

21,000 

C.  El.  St.  Ry.  Lt. 

&  Pw  Co 

M 

48 

101 

Term. 

Knoxville  

82,700 

K.  Tr.  Co  

24 

80 

40- 

Roebling 

2-0 

3  ret.  feed... 

100 

Copper.. 

4-0 



102 

Wis.. 

Madison  

M.  Tr.  Co  

no- 

1-0 

None  

SEVER:  UNDERGROUND  CONDUCTORS. 


290 


{Concluded). 


3 

5 

i 

1 

49 

a 

& 

o    « 

+J 

r 

03  C8 

|C 

1 

irea  is  drai 

power  stat 

um  c  u  r  r 
rom  each. 

1 

g 

a 

Nature 
of  soiL 

Nature 
of  corro- 
sion. 

Extent 
of  corro- 
sion. 

Any  claim 
against 
railway 
company  ? 

What  remedy 
applied  ? 

Effect  of 
remedy. 

a 

m 

•g   a 

1 

2 

i 

1 

i|i 

.5 
& 

No... 

None. 

2 

500 

400 

Gravel, 

No  

No... 

No... 

None. 

6 

None  .... 

No  

9 

8  000 

100 

Noue  .... 

Some  

None  

No... 

Yes.. 



4 

1,500 

150 





None  .... 

No  



No... 

No... 

None  . 

1 

1,400 

400 





None.... 

Yes  

None  



No... 

No... 

None. 

2 

1,500 

400 

Fav.... 

Due  to 
soil.... 

Some  — 

Yes  

Improved 
bonds.  . 

Cons  idera- 

ble    im- 

provem't. 

Pipes 

Yes.. 

1 

800 

450 





Some.... 

Yes  

Tap    pipes    to 
Station  NA      tnnre 

trouble. 

300 


SEVER:     UNDERGROUND  CONDUCTORS. 


TAB 
SUMMARY  OF  MUNICIPAL 


Number.  \ 

00 

1 

I 

S 

£ 

| 

Was  electrolysis 
alleged? 

2 

L 

i! 

5 

• 

$ 

Was  electric  railway 
company  blamed? 

1 

2 

5 

e 

7 
8 
9 
10 
11 

5! 

14 

!S 

17 
18 
19 
20 
21 
22 
23 

24 

25 
26 

27 

28 
29 

Conn  . 
Conn. 
Ill  .... 
Ind.... 

M5..'!.' 
Mass.. 
Mass  .. 
Mich  . 
Minn.  . 
Minn.  . 

Minn.. 
Mo.... 
Mo.... 

N.  J.. 
N.Y.. 
N.  Y.. 
N.  Y.. 

Ohio.. 
Ohio.. 
Ohio.  . 
Ohio.  . 
Pa.... 

Pa.... 

R.I  .. 
B.I  .. 

Wis  .. 

Wis  .. 

v».... 

Hartford  .... 
Middletown.. 

1901 
1902 
18% 

Council              

Water  Commas  

Yes.. 
Yes.. 

Water  . 
Water  . 
Water  . 

Yes.. 
Yes.. 
Yes.. 

Vfts 

[ndianapolis. 
Newport  — 
Baltimore 

1901 
1902 
1901 

Yes 

City  

Water  Works  Com.  .  .  .  Yes.  .  Water  .  i  Yes.  . 
Ch  Eng  Elec  Com       Snm»                 VAC 

Chelsea  
Worcester 

1902 
1901 

City  .  .  . 

Water  Comm'rs  
City  Engineer  

Yes..  Water.  Yes.. 

No 

Detroit 

1896 
1901 
1901 

1903 

1894 
1908 

1901 

Bd.  Water  Comm'rs. 

City  Engineer 

Yes.. 

Little 

Yes.. 

Yes.. 
Yes.. 
Yes.. 

No  .. 

Water  .  Yes.  . 

Gas       i 

Minneapolis  . 
St.  Paul.  

St.  Paul  
St.  Joseph... 
St.  Louis.... 

Newark  .... 

City  Engineer  

Water  Comrn'r  
City    

D.    B.    Maury,    G.    H. 
Benzenburg  &  Co  

Water  Comm'rs  . 

Water. 
Water 

Water, 

gas  .. 

Yes.. 
Yes.. 

Yes.. 

Water  Department. 

City  Electrician  
E.  E.  Brownell  

Engineer  Water  Dept. 
Supt.  Bur.  of  Water.. 
Chief  Engineer  

Albany  

19011  
1901  '  

1898.  . 
No  .. 

Water.  Yes.. 

Rochester... 
Cincinnati  .  .  . 
Cleveland  .  .  . 

1901  Com.  Public  Works.. 
1899  Am.  Soc.  Mun.  Irn..  . 
1899  

E  A  Fisher  

Yes 

Water.  Yes.. 

Com  Waterworks... 

No  .. 

Supt.  Water  Works.  .  . 
F  C  Caldwell 

Yes.. 

Water  . 

Yes.. 

PiiVilin   Wnrks    

Dayton  
Philadelphia. 

Reading  

Pawtucket.. 
Providence  . 
Madison 

1899 
1899 

1900 

1900 

1H9fl 



Ch  Elec  Bureau    .  . 

No 





A.  A.  Knudson  

A.  A.  Knudson  
A.  A.  Knudson  
City  Water  Works  .... 

Q.  H.  Benzenburg  
A.  Schoen  

Yes.. 

Yes.. 
Yes.. 
Yes.. 
i 
Yes.. 
Yes.. 

Water  . 

Water  . 
Water  . 
Water  . 

Water  . 
Water  . 

Yes.  . 

Yes. 
Yes. 
Yes. 

Yes! 

City  Engineers  
Com.  Public  Works. 

Racine  

Richmond... 

1899 

Supt.  Water  Works. 

SEVER:  UNDERGROUND  CONDUCTORS. 


.301 


LE  II. 

REPORTS  ON  ELECTROLYSIS. 


$ 

f! 

» 

*d**- 

s-g 

a 

Was  legal  action  In-  1 
stigated? 

Plaintiff. 

Better  return  

No  more  trouble  

Double  trolley  

Yes.. 

Peoria  Water  Co. 

Reduced  P    D  's 

• 

. 
Reduced  P   D  's 

Yes 

Efficient  return, 

Connected  track    and 

pipes 

Yes.. 

302 


SEVER:     UNDERGROUND  CONDUCTORS. 


TAB 
SUMMARY  OP  MUNICIPAL  ORDINANCES 


1 

fc 

j 

City. 

' 

Immediate 
cause  for  or- 
dinance. 

System  required. 

Are  taps  from  pipes  I 
to  rails  allowed? 

Is  drainage  in  -j-  area 
allowed  ? 

« 

ll 

<o£ 
^ 
a  ce 

|I 

fl 

1 

Conn  .  . 

Montville  

9 

D   O... 

Double     trolley    o  r 

3 

111... 

1900 

4 

Ill  

5 

Ga... 

Atlanta  

1898 

fi 

Mass 

7 

Mich    . 

Battle  Creek  

Double   trolley  if  de- 

No 

R 

N  J..  , 

Atlantic  City  

1WI 

No 

No 

No 

0) 

N  Y  . 

N  Y  city   

10 

¥&  .... 

Altoona  

1909 

11 

Pa  .. 

Philadelphia  

1° 

Va  .... 

1fi% 

SEVER:  UNDERGROUND  CONDUCTORS. 

LE  III. 

CONCERNING  ELECTROLYSIS. 


30;} 


a 

•31  • 

ft 

ft 

•  as 

•  w 

•rt 

<i>  L| 

Is  railway  com- 
pany made  lia- 
ble for  corro- 

ifl 

Fj,9 

HR 

Allowable    leakage 
of  current. 

ii 

Remarks. 

sion? 

=>£ 

e8  g 

p,T3 

ti® 

^9 

O 

*D  S* 
S  ft 

D  9* 

eS  ft 

0 

0^ 

S 

a 

Q 

Q 

not    less    than  + 

feeders. 

1 

1 

7<&-300' 

8.8 

AH  damage    to 

water    and   gas 

V( 

No  mor6  than  ono 

74 

amp  in  any  pips 

i^_200' 

8  8 

Yes 

'4 

Jl^ 

VA  200' 

A  A 

74 

25 

Electric  code  of  city 

Yes.  

No  leakage  

department. 
Periodic  tests  and  ex- 

cavations. 

i/ 
™ 

^ 

^6-200' 

8  I 

Ye&.  «... 

304 


SEVER:     UVDEKGKOUXn  CONDUCTORS. 


w 


-1    as 
H    § 


4  A'lpA'qpenAvo 
sadid  aa^uM.  aoy 


i 


Now 


O  D  CD  Q)  & 

fl  P4  fl  fl  fl        C 

gggig  ^ 


fe     IISS      &ogWS      hhfc-|     "r     H 

E?    fefelb    b^g^b    bb^Ufe    S.2    fe 


oa  Illl  islsl"  sss^^  06  oo£ 


^^JQ, 

OJ3     .-S.-S3 


ford 


1 1 1 II  si  ii  ai 

II  5SSS  ^I3£  &8&Z  £3  5^5  5IS 


33  3Sls 


3S     SSS 


i-oooJO^H     o*ecTjoo«o 


SEVER:     UNDERGROUND  CONDUCTORS. 


305 


•s-g 


:«   ^JH   *   K2 


5.9  .2 
oo 


S 


33    3 


ET-EC.  RYS. 20. 


306 


SEVER:     UNDERGROUND  CONDUCTORS. 


TAB 

SUMMARY  OF  EXPERT  OPINION 


Number. 

Name  of  expert. 

Title  of  article. 

Where  published. 

I 

tssi 
i|  1 

Most  suitable 
remedy. 

1 
8 

i 

I 

11 

12 

13 

14 

15 
16 

17 

IS 

19 
20 
21 
22 
23 

s 

A.  V.Abbott... 
Bavlis.  .  . 

Electrol.  from  Ry.  Cur.  . 
Electrolysis  

1899 

Yfts.  .  . 

Canadian  Elec.  Assn. 

1894  No  

....IT-,.... 

Only     cure     is 
double  trolley.. 

Wm.  Brophy.... 

H.  P.  Brown  .... 
Ellicott  

Prevention  of  Electrol.. 
Remedy  for  Electrol.  .  .  . 

IfW 

Neg.  booster  

Report  in  Chicago  .  . 

T   H   F'arnhftTn 

Cassiers1  Mag       .  . 

1895 
18<M 

Yes 

Fisher  

Legal  Status  

A  B  Herrick 

D.  C.  Jackson...  .1  Electrol.  of  iron  Pipes.  . 
....  Corrosion  of  Iron  Pipes. 
Kalsey         .             -                        

1894 

Yes 

Report  to  Salt  Lake 
City  

H.  R.  Keithley  .  . 

A.  A.  Knudson..  . 
G   Low  

How  to  Prevent  Electrol. 

Corros.  of  Metal  by  Elec. 
Rail    Bonding    &   Elec. 

Street  Ry.  Review  .  . 
Amer.  Elec-ch.  Soc.  . 

1894 

1903 
1895 

No  
No  

Complete    metal 
circuit 

Double  trolley... 

M.  R.  McAddo... 

1 

W.  H.  Merrill.... 

C.  H.  Morse  .  .  . 
O'Reilly  

Electrol.  of  Buried  Pipes 
Electrol.  of  Water  Pipes 

Western  Electric.... 
Street  Ry.  Review  .  . 

1896  Yes.  .  .  . 
..  Xo... 

Double  trolley  4 
drainage  

Report  to  St  Louis    1896 

Parshall  

Electrolysis  

Jour.  Inst.  of  E.  Es..  1898 
Incor.  Gas  Inst.  Eng.  1902 
1901 

Yes.... 

J.  Swinburne  — 
Stone  &  Webster 
H.  C.  Townsend.. 

Electrol.  of  Gas  Mains.  . 
Rochester  Report    .      . 

Cassiers'  Mag             1ftQS 

Double  trolley... 

Results  of  Electro!  
More  About  Electrol.  .  .  . 
How  to  Cure  Electrol.  .  . 

Boston  Report  
Street  Ry.  Review  .  . 
Street  Ry.  Review  .  . 

1895 
1893 
1894 

Yes 

Yes.... 

Yes.  .  .  . 

SEVER:  UNDERGROUND  CONDUCTORS. 


307 


LE  V. 


ELECTROLYSIS. 


3* 

2r* 

f- 

£5 

£* 

.| 

*•§ 

53 

o'o 

i||> 

|i 

II 

Requirements  as  to 
return   feeder 
system. 

Are  taps  from 
rails  to  pipes 
recommended? 

!i 

a  o 

c  £ 

II 

a  £ 

ll» 

Remarks. 

§--2 
OS^' 

P 

1} 

Ii 

•^ 

Good 

Good   . 

Yes.. 

Good  .  . 

pipe  joints. 

Yes... 

Good  .  . 

Good  .  . 



No  

Yes.. 

No... 

. 

Yes.. 

Suggests  balanced 
feeder  system. 

Good  .  . 

Good  .  . 

-}-  Area  

Along  entire  tracks 

Yes  

Advises  good  bonding 

for  comp.  met.  cir. 

Good 

Good   . 

Yes 

Cood  .. 

Good  .  . 

Good  

Yes.. 

Yes 

Yes.. 

With  precaution 

Almost  no  trouble  in 

St.  Louis. 

Good  .  . 

Good  .  . 



No  

Yes.. 

Good  .  . 

Good   . 

Yes 

Yes 

Yes.  . 

Yes  . 

Good  .  . 

Good.. 

Good  

Yes  





Good.. 

Good.. 

Good  

Yes.. 







30cS  SEVER:     UNDERGROUND  CONDUCTORS. 

DISCUSSION. 

Mr.  JOHN  HESKETH:  Being  in  the  position  of  having  had  experience 
on  both  sides  of  the  problem  I  have  had  reason  to  give  the  question  very 
close  study.  There  are  certain  well-defined  lines  and  conclusions  from 
which  I  think  we  cannot  escape.  To  begin  with,  the  onus  of  protecting 
underground  works  from  electrolysis  or  from  damage  by  tramway  systems 
cannot  possibly  be  considered  as  resting  on  one  or  the  other  party  ex- 
clusively. It  must,  if  it  is  to  be  a  successful  work,  be  a  mutual  one.  It  is 
impossible  for  the  telephone  company,  even  by  the  adoption  of  all  known 
reasonable  methods,  to  protect  their  works  if  the  tramway  company,  on 
their  part,  neglect  well-known  methods.  Further,  it  is  impossible 
for  the  tramway  company  to  so  run  their  system  as  to  avoid  damage,  if 
the  telephone  company  or  others  interested  are  laying  their  works  in 
an  unnecessarily  dangerous  manner.  As  an  instance:  In  one  case  which 
I  have  in  mind,  a  water  company  laid  its  lead  service  pipes  within  six 
inches  of  the  rails  of  a  tramway  system.  They  invited  electrolysis;  they 
got  it;  and  then  they  complained.  Further,  there  are  conditions  which 
are  easily  imaginable,  where  a  system  of  water  pipes  acts  as  a  feeder 
from  the  zone  in  which  danger  is  existent  to  a  zone  which  otherwise 
would  not  be  dangerous.  In  such  cases  the  water-supply  company,  or  the 
gas  company,  should  so  insulate  its  pipes  as  to  prevent  the  feeding  of 
danger  from  the  one  zone  into  the  other.  Further,  it  has  been  the  effort 
in  one  or  two  places  to  prevent  damage  by  laying  down  hard  and  fast 
rules  as  to  the  drop  in  the  return  circuit.  For  instance,  the  Board  of 
Trade  of  London  laid  down  an  arbitrary  figure  of  seven  volts  as  the 
maximum  difference  of  potential  between  the  ends  of  the  return.  But 
any  figure  of  drop  in  the  return  must  take  into  consideration  the  length 
of  the  line.  It  is  not  necessarily  the  drop  along  the  return  that  does  the 
damage.  It  is  rather  the  difference  of  potential  between  the  return  and 
the  other  metal  bodies  in  the  neighborhood;  and  yet  not  altogether  so. 
It  is  not  the  difference  of  potential  only,  but  the  capacity  for  current 
carrying  from  the  return  into  the  pipe.  There  may  be  a  huge  difference 
of  potential  and  yet  no  passage  of  current  into  the  pipe.  There  may  be 
a  very  small  difference  of  potential,  and  yet  a  very  dangerous  current. 
There  we  strike  another  main  principle  —  the  method  of  testing  for  pos- 
sible danger,  which  ought  to  be  clearly  defined.  It  is  not  sufficient  to 
measure  the  difference  of  potential  between  the  pipe  and  the  return.  I 
rather  incline  to  the  belief  that  the  method  which  has  during  the  past 
year  been  suggested  in  Germany,  of  measuring  the  difference  of  potential 
between  the  rail  and  the  earth  nearest  to  the  rail,  is  a  more  correct  method. 
It  takes  into  account  the  electrolyte  between  the  two  bodies. 

Recently  the  Australian  Government  met  in  conference  the  engineers  of 
the  telegraph  department  and  engineers  representing  electric  supply  indus- 
tries. In  conference,  we  agreed  on  certain  regulations  for  the  protection 
of  the  works  of  the  Postmaster-General  of  Australia,  and  the  points 
just  mentioned  were  the  salient  points  brought  out  in  the  discussion  on 
the  question  of  electrolysis.  When  I  heard  that  this  Congress  was  to 
be  held,  it  appeared  to  me  as  rather  desirable  that  an  effort  be  made  to 


SEVER:     UNDERGROUND  CONDUCTORS.  30C 

have  an  expression  of  opinion  from  the  technical  associations  of  different 
nations  on  this  most  important  subjejct,  and  I  mention  that  now  for  your 
consideration,  if  deemed  advisable.  It  is  rather  a  problem  as  to  how 
such  an  expression  of  opinion  could  be  obtained,  but  it  seems  to  me,  in 
view  of  the  diversity  of  regulations  throughout  the  world  and  the  lack 
of  authoritative  statements  based  on  a  scientific  principle,  that  such  a 
statement  prepared  by  scientific  bodies  would  be  invaluable  to  both  sides. 

Prof.  F.  C.  CALDWELL:  In  Columbus,  Ohio,  as  has  been  mentioned  by 
Prof.  Sever,  we  have  made  some  investigation  of  this  matter,  and  our 
conditions  there  are  particularly  favorable  for  absence  from  the  trouble. 
I  believe  the  soil  there  is  not  such  as  to  produce  much  electrolysis,  and 
the  lay  of  the  railway  system  is  particularly  favorable  for  freedom  from 
it.  It  seems  to  me  there  are  two  points  upon  which  definite  information 
is  needed  in  connection  with  this  matter  of  electrolysis.  The  first  is 
whether  we  should  look  for  trouble  only  where  the  current  leaves  to  go 
to  other  metallic  structures,  or  whether  we  are  to  look  also  to  the  joints 
of  the  pipes.  There  is  much  difference  of  opinion  upon  this  question.  It 
has  been  claimed  that  trouble  has  been  found  at  the  joints,  but  on  the 
other  hand  we  find  engineers  taking  very  decidedly  the  stand  that  ,all 
that  is  necessary  is  to  keep  the  current  from  leaving  the  pipes  and 
going  to  other  conducting  material.  Information  on  this  subject  would 
certainly  be  very  valuable.  The  second  point  is  as  to  how  much  current 
can  be  allowed  in  the  pipes  or  to  leave  the  pipes.  This  is  especially  im- 
portant if  it  is  true  that  we  are  to  look  for  trouble  at  the  joints.  If  we 
must  keep  the  current  out  of  the  pipes  practically  altogether,  then  it 
becomes  an  important  matter  to  know  how  much  current  can  be  allowed  to 
flow  and  still  not  add  an  appreciable  amount  to  their  disintegration.  There 
has  been  a  little  data  along  this  line  published  in  regard  to  the  resistance 
of  pipes.  What  is  needed  is  data  as  to  the  resistance  in  the  case  of  pipes 
laid  in  dry  sandy  soil.  Where  a  pipe  is  laid  through  a  street,  if  we  make 
an  attempt  to  measure  its  resistance  we  shall  get  the  joint  resistance 
of  the  pipe,  the  surrounding  soil,  and  other  conducting  material,  so  that 
we  cannot  be  sure  that  the  resistance  we  get  would  show  the  current 
going  through  the  pipe. 

The  other  question  as  to  how  much  damage  is  to  be  expected  from  the 
current  when  it  leaves  the  pipe,  I  believe,  depends  very  much  upon  the 
surrounding  soil.  In  some  cities  much  more  damage  may  be  anticipated, 
with  the  same  current  flowing,  than  in  others.  We  have  been  carrying 
on,  at  the  Ohio  State  University,  some  investigation  along  this  line,  ob- 
taining earth  from  different  cities  and  using  an  electrode  which  was 
weighed  before  and  after  the  test.  Our  results  so  far  have  not  been 
sufficient  to  warrant  any  conclusions,  but  they  are  interesting.  We  have 
found  in  two  different  tests  a  considerable  difference  in  the  amount  of 
material  in  different  cities.  Soil  from  Dayton,  Ohio,  where  there  has 
been  much  trouble,  gave  a  large  amount  of  electrolysis,  while  that  from 
Columbus  gave  a  very  small  amount.  It  looks  as  if  this  was  an  important 
point  to  be  considered. 

Mr.  H.  E.  HARRISON  :  It  does  not  matter  practically  how  much  current 
or  what  current  density  flows  into  a  pipe.  It  has  been  assumed  that  the 

\ 


310  SEVER:     UNDERGROUND  CONDUCTORS. 

current  flowing  into  the  pipe  would  come  out  more  or  less  uniformly 
through  the  whole  service;  but  I  do  not  believe  this  is  so.  The  pipe  may 
pass  through  a  considerable  length  of  soil  which  will  be  a  very  fair  in- 
sulator, and  will  then  come  upon  a  patch  of  soil  that  is  conductive  to  a 
high  degree,  with  the  result  that  the  current  density  is  more  visible  and 
the  damage  greater. 

Prof.  SEVER:  The  data  which  we  have  collected  contains  many  refer- 
ences to  underground  conductors  other  than  piping  systems,  so  that  I 
think  it  is  perfectly  proper  that  that  phase  of  the  situation  should  be 
brought  before  this  meeting.  About  two  years  ago,  when  I  became  con- 
nected with  the  city  government  of  New  York,  Mr.  Jones  brought  me  a 
cable  sheath  which  he  claimed  had  been  destroyed  by  electrolysis.  I  know 
that  on  some  cable  sheaths  in  New  York  city,  both  on  the  telephone  and 
the  power  circuits,  there  are  large  currents  coming  presumably  from  the 
operation  of  the  electric  railways.  In  the  Bronx  there  has  been  con- 
siderable difficulty.  In  the  borough  of  Manhattan  there  has  been  diffi- 
culty which  to  some  extent  has  been  remedied  by  the  co-operation  of  the 
officials  of  the  railway  company  and  the  telephone  companies.  I  know  of 
one  instance  where  the  sheaths  were  bonded  at  one  point  by  a  heavy 
copper  conductor  to  a  return  of  the  Manhattan  "  L," —  approximately  1500 
amperes  passed  over  that  wire  —  sufficient  to  heat  it  so  one  could  not  put 
his  hand  upon  it.  The  Manhattan  elevated  road  uses  its  structure  com- 
pletely bonded,  its  service  rails  completely  bonded,  and  a  large  amount  of 
return  feeder,  something  like  six  or  seven  million  circular  mils,  to  get 
their  current  back  without  causing  trouble  to  their  own  and  other  con- 
ductors. In  spite  of  all  their  precautions,  there  are  still  thousands  oi 
amperes  coining  back  on  their  cable  sheaths  as  well  as  those  of  other 
companies.  It  has  been  drawn  to  the  attention  of  the  city  officials  for 
their  recommendation,  as  there  are  at  times  a  higher  potential  than 
twenty-five  volts  between  the  end  of  the  line  and  the  nearest  sub-station, 
which  is  the  maximum  fixed  by  the  city  rules. 

Mr.  P.  B.  DELANY:  It  seems  to  me  there  is  one  phase  of  this  subject 
which  has  been  overlooked,  and  that  is  the  shunting  of  water  and  gas 
pipes  or  the  cable  sheath,  by  the  grounding  of  telegraph  wires  in  the  city. 
This  may,  to  a  certain  degree,  account  for  the  apparent  discrepancies 
electrolytically,  in  different  cities  and  towns  and  through  different  soils. 
We  all  know  that  there  is  in  many  places  a  very  great  leakage  —  what 
we  call  stray  or  vagrant  currents  —  into  the  telegraph  circuits  by  way 
of  the  ground  return.  I  myself  have  had  experience  with  wires  about 
a  hundred  miles  in  length,  and  it  was  rather  a  disagreeable  experience.  I 
tried  some  synchronous  experiments  four  years  ago,  and  I  found  there 
was  a  voltage  varying  from  three  or  four  volts  to  seventy-five  in  that 
circuit  —  not  constantly,  but  running  up  and  down.  If  it  had  been  con- 
stant, we  might  have  been  able  to  do  something  with  it,  but  as  it  was 
fluctuating,  it  was  rather  disastrous  to  the  experiments  at  the  time.  It 
has  occurred  to  me  that  in  cities  where  there  are  hundreds  of  ground 
connections  made  at  different  points  to  the  pipes  and  where  considerable 
electric  energy  is  used  in  the  operation  of  telegraph  lines  grounded  in 
cities,  some  of  the  electrolysis  may  be  even  due  to  that  source,  as  well  as 


SEVER:     UNDERGROUND  CONDUCTORS.  311 

the  protection  of  the  pipes  from  power  leakage  by  the  shunting.  I  think 
this  suggestion  may  throw  some  light  on  the  subject,  although  I  presume 
that  this  phase  of  the  case  has  been  taken  into  consideration  by  Mr.  Sever 
and  his  associates.  It  has  not  been  referred  to  in  the  discussion. 

Mr.  BANCROFT  GHEBABDI:  One  of  the  functions  of  my  department  is 
taking  precautions  against  electrolysis  trouble  on  our  cables,  and  in  that 
connection  the  bulk  of  our  work  has  been  in  Brooklyn,  on  account  of  our 
very  large  underground  plant  there  and  the  great  extent  of  the  overhead 
trolley  system.  It  is  not  unusual  for  us  to  have  to  take  care  of  currents 
as  great  as  200  or  300  amperes  at  a  single  point  on  our  system.  This 
shows  that  the  aggregate  amount  of  current  that  our  system  is  carrying 
back  to  the  power-houses  amounts  to  thousands  of  amperes.  There  is  a 
certain  expense  in  connection  with  this  work  which  is  quite  appreciable, 
and  there  still  remains,  after  everything  is  done  that  we  can  do,  a  certain 
amount  of  trouble  which  is  real  trouble.  The  discussion  of  the  respon- 
sibility for  such  trouble  and  expense  is  one  that  it  seems  to  me  is  beyond 
the  scope  of  this  section  and  I  shall  not  touch  on  it  here. 

Prof.  SEVER:  In  connection  with  the  situation  on  the  Virginia  Pas- 
senger &  Power  Company,  at  Richmond,  Va.,  Mr.  Stillwell  went  at  the 
matter  in  an  engineering  way  by  laying  out  very  carefully  on  paper  the 
whole  railroad  system,  placing  the  cars  in  accordance  with  their  various 
schedules,  and  ascertaining  those  points  to  which  he  could  most  profitably 
connect  a  return  conductor.  He  decided  upon  four  points  about  the  city, 
almost  at  the  corners  of  a  rectangle,  and  carried  directly  back  to  the 
power  station  very  heavy  return  feeders,  as  well  as  heavily  bonding  the 
tracks.  From  the  results  which  they  are  getting,  it  would  seem  that 
that  is  a  very  satisfactory  way  in  that  particular  locality  to  solve  the 
problem.  Chemical  analyses  were  made  also  of  the  soils.  I  learned  from 
him  a  short  time  ago  that  the  city,  through  its  engineering  staff,  ap- 
proved of  this  scheme  and  accepted  the  efforts  on  the  part  of  the  railroad 
company  as  an  expression  of  a  desire  to  reduce  the  trouble.  As  stated  in 
one  of  the  tables  which  is  presented,  the  city  of  Richmond  insists  that 
the  railroad  company  must  pay  for  all  damage  to  pipes.  How  two  men 
are  going  to  agree  as  to  whether  damage  is  due  to  electrolysis  or  to 
ordinary  tubercular  action  or  rust,  I  do  not  know,  and  I  do  not  know  any- 
body who  does  know  definitely.  The  other  day  we  took  up  in  Brooklyn 
cast-iron  water  pipes,  which  had  been  down  fifty-two  years,  so  filled  with 
tubercular  nodules  that  the  area  of  the  pipe  was  reduced  to  about  one-half 
of  its  original  area.  In  other  places  we  took  up  lead  pipe,  part  of  which 
had  entirely  disappeared,  undoubtedly  through  electrolytic  action. 

Mr.  J.  SIGFRID  EDSTR'OM:  We  have  had  very  little  trouble  in  Europe 
from  electrolysis.  There  has  been  some,  however,  in  the  earliest  railroads 
built  in  England,  but  lately  we  have  experienced  hardly  any  trouble.  I 
think  this  is  owing  to  the  very  solid  construction  in  bonding  and  in  cables 
carrying  return  current  to  the  central  station.  In  Berlin  the  city  officials 
require  that  there  shall  be  no  larger  voltage  between  any  two  points  of  the 
rails  in  the  city  system  than  two  volts  —  that  is,  between  any  points  in  the 
rail  system  of  the  tramway  there  must  be  no  greater  pressure  than  two 
volts.  This,  or  a  similar  stipulation,  has  been  adopted  by  many  other 


312  SEVER:     UNDERGROUND  CONDUCTORS. 

cities,  including  cities  in  Switzerland  and  Sweden,  where  I  have  had  the 
pleasure  to  be  a  railway  engineer.  In  these  places  we  bond  the  rails  with 
two  heavy  copper  wires  at  each  joint.  We  have  double  track  generally, 
and  consequently  we  have  eight  copper  wires  at  each  double  pair  of  joints 
of  the  rails.  We  bond  the  rails  between  each  other  and  also  the  tracks 
at  certain  distances.  At  crossing  of  bridges  or  water  pipes,  where  the 
rails  get  close  to  iron  in  the  earth,  we  insulate  the  rail  with  asphalt  as 
much  as  possible.  The  rails  themselves  in  the  street  are  generally  in- 
sulated through  a  layer  of  stones  or  concrete  put  under  the  rails.  To  take 
the  current  from  the  rail,  we  put  it  in  an  insulated  cable  of  very  heavy 
dimensions.  It  is  very  important  to  have  the  cable  insulated",  as  a  bare 
copper  cable,  which  I  know  is  often  used  and  which  generally  is  buried 
deep  into  the  street,  invites  the  current  to  seek  other  ways  home.  The 
general  practice  in  Europe  is  that,  where  a  feeding  cable  is  connected  to  a 
certain  part  of  the  overhead  wires,  a  return  insulated  cable  of  the  same 
dimensions  as  the  feeding  cable  is  used.  This  has  also  the  advantage  that 
in  case  the  positive  cable  becomes  damaged,  we  can  easily  exchange  it  for 
the  return  cable  until  the  positive  cable  has  been  repaired.  All  the  nega- 
tive returns  are  carried  into  the  station  through  resistances,  and  these  are 
regulated  so  that  the  actual  current  for  which  the  cable  is  assigned  arrives 
there;  thus  the  current  is  split  up  and  no  cable  is  overloaded.  In  this 
way  every  feeding  point  becomes  a  "  central  station."  These  central  sta- 
tions are  planted  around  in  the  city,  and  we  have  no  long  flows  of  current 
running  through  the  city.  Street  railways  built  ten  years  ago  in  this  wajT 
have  given  no  trouble  whatever. 

As  to  disturbances  on  telephones  in  cities,  where  the  telephones  use  the 
earth  as  a  return,  there  has  been  some  slight  disturbance,  as  naturally 
a  portion  of  the  street-car  current  must  go  through  the  earth  and  thus 
some  of  it  also  through  the  telephone  wires.  In  cities  where  we  have  a 
double-wire  telephone  system,  there  is  no  trouble  whatsoever. 

Mr.  HESKETH  :  Although,  as  you  stated,  the  regulations  define  the  drop 
in  voltage,  I  should  like  to  ask  what  in  actual  practice  is  found  to  be  the 
approximation  to  the  regulation?  How  closely  in  Berlin  do  they  comply 
with  the  regulations?  It  would  be  interesting  to  know,  for  the  purposes  of 
comparison  simply,  some  of  the  leading  dimensions  of  the  system  on  which 
the  regulations  mentioned  are  found  practicable  —  the  mileage  of  track  and 
the  number  of  amperes  output  from  the  station  per  mile  of  track. 

Mr.  EosTRbM  :  I  am  here  not  loaded  with  figures,  but  I  will  try  to  give 
part  of  the  information.  When  the  plant  is  laid  out,  it  is  laid  out  accord- 
ing to  a  certain  schedule,  and  consequently  you  know  the  loads  on  the 
several  points  of  the  city.  According  to  this  the  dimensions  of  the  cables 
are  figured  out.  The  track  itself  has  the  ordinary  two  heavy  copper  wires 
at  each  rail  and  four  rails  at  the  side  of  each  other  are  considered  to  be 
sufficient  for  the  two  volts  drop  that  should  be  the  maximum  in  the  city. 
Actual  tests  have  not  been  taken,  so  far  as  I  know.  I  have  myself  been 
opposed  to  the  two  volt  requirement,  as  I  consider  this  limit  very  low, 
and  I  do  not  think  that  on  any  day  of  heavy  traffic  —  for  instance,  Sun- 
days or  Easterdays  or  Whitsundays  —  that  the  two  volts  will  be  the  limit. 
but  that  you  will  actually  find  the  drop  far  larger. 


SEVER:  UNDERGROUND  CONDUCTORS.         313 

CHAIBMAN  JONES:  I  perhaps  might  give  you  a  few  salient  facts  of  the 
effect  of  electrolysis  upon  the  Postal  Telegraph.  The  Postal  Telegraph 
Cable  Company  would  be  only  too  glad  to  submit  any  of  the  data  it  has 
upon  the  subject  of  destruction  of  their  cables  by  electrolysis  to  Prof 
Sever  for  the  purposes  of  his  paper.  I  think  they  would  do  this  in  the 
interest  of  electrical  engineers  everywhere,  and  in  the  interest  of  munic- 
ipalities whose  pipes  are  being  eaten  up,  and  also  our  good  neighbors,  the 
telephone  people,  who  are  in  the  same  boat  with  us  in  that  respect. 

I  can  only,  of  course,  as  intimated,  speak  in  a  general  way  on  the  sub- 
ject. The  telegraph  companies  were  urged  to  place  their  wires  under- 
ground, commencing  about  the  year  1880.  Cities  got  tired  of  the  crow's 
nests  and  networks  of  wires  which  were  in  their  streets.  Some  of  them 
were  curiosities.  Commencing  with  New  York,  Philadelphia,  and  other 
cities,  the  agitation  became  so  great  that  eventually  they  started  to  put 
in  their  wires  underground.  As  a  rule,  the  cables  of  the  telegraph  com- 
pany are  not  to  be  compared  with  the  network  of  water  pipes  and  gas 
pipes  of  cities,  nor,  except  in  a  few  cases,  the  rails  of  the  tramways.  The 
telegraph  companies  coming  into  a  city  and  passing  through  generally 
follow  a  line  of  pipes,  and  lately  the  line  of  rails  of  the  electric  railroads, 
and  we  have  had  a  great  deal  of  trouble  from  electrolysis,  in  times  past, 
in  various  cities,  commencing  with  Boston,  Hartford,  Baltimore,  Chicago, 
Atlanta,  New  Orleans,  and  other  places.  In  almost  all  those  places,  our 
cables,  that  had  been  laid  parallel  with  or  near  to  the  electric  railroads, 
have  been  attacked,  and  sections  have  been  eaten  up,  and  our  service 
stopped.  We  were  helpless  in  the  matter,  because  the  cities  in  some  cases 
had  ordered  us  underground,  and  after  having  gone  underground,  our  poles 
were  taken  down,  and  it  was  not  possible  to  place  the  poles  up  again  and 
put  the  wires  on  them  very  oxpeditiously ;  so  we  had  to  suffer  and  so 
the  public  had  to  suffer.  Its  telegrams  could  not  be  forwarded  until  we 
had  made  the  repairs.  We  found  out,  however,  that  by  applying  the  now 
universal  remedy  of  bonding,  where  we  could  secure  a  good  return  wire 
from  the  point  at  which  the  currents  were  leaving  our  cable  sheaths  to 
get  back  to  the  negative  brush  of  the  generating  station  of  the  railroad 
companies,  we  were  rendered  entirely  immune.  We  have  not  had  any 
trouble  since  we  have  been  properly  bonded  in  any  city.  Quite  recently, 
in  New  Orleans,  our  cable  was  attacked  at  one  point;  but  we  have  since 
bonded  and  I  think  there  will  be  no  further  trouble.  In  Hartford  we  have 
for  some  years  been  bonded,  and  no  trouble  has  arisen  there.  In  all  -other 
places  where  we  have  been  properly  bonded  there  has  been  no  trouble.  It 
of  course  follows  that  the  currents  which  are  carried  through  the  trolley 
pole  and  down  into  the  motor  of  the  car  and  so  into  the  rails,  is  seeking 
its  way  back  to  the  generating  station,  and  if  the  resistance  is  very  high 
between  the  point  where  the  car  is  resting  upon  the  tracks  and  the  negative 
brush  of  the  machine  at  the  station,  it  is  going  to  seek  a  great  many  ways 
to  get  back.  It  will  go  all  around  and  follow  every  route  that  is  possible. 
As  a  matter  of  fact,  we  loan  the  sheaths  of  our  cables  to  the  railroad 
companies  to  allow  them  to  get  their  current  back  to  the  station,  and  we 
bond  our  sheath  to  their  return  wire  so  they  can  have  every  use  of  it  and 
get  back  the  easiest  way  possible.  We  do  that  to  prevent  getting  hurt. 


314         SEVER:  UNDERGROUND  CONDUCTORS. 

It  is  not  where  their  current  comes  on  and  starts  in  to  go  back  that  we 
suffer,  but  it  is  where  the  current  leaves  our  sheath  to  go  through  moist 
ground  or  some  electrolyte  to  reach  the  metallic  conductor  at  the  power 
station;  so  that  we  have  found  it  was  necessary  for  us  to  make  that  path 
just  as  good  as  possible.  Our  sheaths  are  one-eighth  of  an  inch  lead  with 
10  per  cent  of  tin,  and  we  have  not  yet  had  a  case  where  the  carrying 
capacity  has  been  exceeded  by  the  amount  of  current  that  our  friends, 
the  railroad  people,  want  to  have  us  carry  back  for  them.  It  is  lying 
there,  doing  us  no  good  at  all,  and  we  feel  no  effect  from  any  induction 
in  that  respect,  and  we  are  glad  enough  not  to  be  eaten  up  in  the  under- 
taking. 

It  is  pretty  difficult  to  tell  whether  there  is  any  serious  electrolysis 
generated  by  telegraph  currents  or  not.  Of  course,  the  companies  are  using 
much  more  current  now  than  ever  before,  on  account  of  their  increased 
business,  but  prior  to  the  time  of  electric  lights  and  trolley  systems,  I 
have  never  yet  heard  of  any  electrolysis  arising  from  telegraph  currents, 
and  do  not  think  they  are  of  sufficient  quantity  to  figure  in  the  case  at  all. 

There  is  another  question,  in  regard  to  alternating  currents  being  used 
for  transportation  or  trolley  purposes.  How  are  we  going  to  be  effected 
when  alternating  currents  are  used?  That  is  an  open  question  which  I  am 
not  prepared  to  discuss,  but  I  would  like  to  call  it  to  your  attention. 


BRAKING  HIGH-SPEED  TRAINS. 


BY  R.  A.  PARKE. 


During  a  hearing  upon  an  application  for  a  charter  for  the 
New  York  &  Port  Chester  Eailroad  Company,,  before  the  New 
York  Eailroad.  (Commission,  some  three  and  one-half  years  ago,  the 
writer  was  called  upon  for  expert  testimony  concerning  the  dis- 
tance in  which  electric  trains  might  be  stopped,  in  regular  ser- 
vice, from  a  speed  of  about  60  miles  an  hour.  It  was  then  that 
expression  was  first  publicly  given  to  the  opinion  that  the  special 
conditions  under  .which  the  brakes  are  applied  upon  trains  of  such 
high  speeds  warrant  a  force  and  promptness  of  application  which 
could  be  employed  at  low  speeds  only  with  serious  shock  and  dan- 
ger of  train  rupture.  For  years  prior  to  that  time,  the  uniform 
teaching  and  recommendation  of  The  Westinghouse  Air  Brake 
Company,  as  given  in  instruction  cars  and  by  authorized  repre- 
sentatives of  the  company,  had  been  emphatically  opposed  to  the 
use  of  what  is  commonly  known  as  the  "emergency  application" 
of  the  quick-action  air  brake  in  ordinary  train  service,  and.  a  propo- 
sition which  contemplated  the  use  of  the  emergency  application 
of  the  quick-action  air  brake,  and  particularly  the  more  powerful 
high-speed  form  of  air  brake,  appeared  to  the  average  railroad 
officer  as  nothing  short  of  heresy.  Members  of  the  Railroad  Com- 
mission promptly  instituted  a  line  of  questioning  which  made  it 
quite  evident  that  they  were  similarly  impressed. 

One  of  the  fundamental  grounds  upon  which  the  New  York  & 
Port  Chester  Railroad  sought  to  justify  the  granting  of  a  char- 
ter for  a  railroad  line  paralleling  a  steam  railroad  already  in 
operation,  was  the  materially  improved  local  express-train  ser- 
vice which  it  was  proposed  to  attain  through  the  superior  rate 
of  acceleration  acquired  upon  electric  trains  by  the  use  of  the 
system  of  multiple  control  of  motors  operating  uppn  the  axles 
throughout  the  train,  and  the  higher  rate  of  retardation  to  be 
obtained  through  the  high  efficiency  of  the  emergency  application 
of  the  air  brake,  in  bringing  such  trains  to  a  station  stop. 

1315] 


316  PARKE:     BRAKING   HIGH-SPEED   TRAINS. 

In  presenting  the  matter  to  the  Eailroad  Commission,,  elabor- 
ately arranged  curves,  indicating  the  rates  of  acceleration  and 
retardation,  had  been  prepared  by  the  able  engineer,  Mr.  C.  0. 
Mailloux,  which  appeared  to  justify  the  claims  for  the  improved 
character  of  train  services  contemplated  by  the  company.  Al- 
though multiple-control  systems  of  electrical  train  control  were, 
at  the  time,  in  successful  operation,  it  did  not  appear  that  the 
rate  of  retardation  indicated  by  the  stopping  curves  had  been  at- 
tained in  regular  service,  and  the  high  efficiency  of  the  proposed 
train  service  was  characterized  as  impracticable  and  chimerical  by 
those  opposed  to  the  granting  of  the  charter. 

It  is  a  notable  fact  that,  while  the  effort  to  attain  high  accelera- 
tion in  bringing  electric  trains  to  the  required  speed  had  in- 
volved costly  extension  of  the  application  of  motors  to  a  number 
of  cars  throughout  the  train  —  being  applied,  in  some  cases,  to 
the  trucks  of  all  the  cars  —  practically  no  effort  had  previously 
been  made  to  realize  a  higher  rate  of  retardation,  in  regular  ser- 
vice, than  that  which  had  been  regularly  employed  in  steam-rail- 
road service,  through  the  service  application  of  the  ordinary  auto- 
matic air  brake.  Without  attempting  any  discussion  of  the  merits 
of  multiple-control  systems  of  electric  locomotion,  or  the  commer- 
cial limitation  of  the  expense  justified  in  extending  the  appli- 
cation of  motors  to  a  number  of  cars  throughout  the  train,  it 
may  properly  be  suggested  that  commercial  economy  may  not  result 
from  an  indefinite  extension  of  such  systems.  The  inadequacy  of 
a  single  motor  car  for  the  acceleration  of  a  train  of  several  cars 
easily  justifies  the  application  of  motors  to  the  trucks  of  one  or 
more  additional  cars,  depending  upon  the  number  of  cars  in  the 
train;  but  it  may  also  be  readily  understood  that  a  point  may  be 
reached,  in  the  increased  acceleration  due  to  multiplication  of 
motors,  beyond  which  the  addition  of  other  motors  is  accompanied 
by  too  small  a  measure  of  increased  acceleration  to  justify  the 
added  expense  of  installation  and  maintenance. 

An  illustration  may  be  found  in  the  operation  of  city  water- 
works' systems.  It  is  a  well-understood  fact  that  refinement  of 
pumping  machinery  is  justified  up  to  the  attainment  of  a  practical 
duty  of  somewhere  in  the  neighborhood  of  90,000,000  gallons;  be- 
yond this,  further  refinement,  whereby  an  increased  duty  is  accom- 
plished, is  attended  by  an  increased  cost  of  plant  and  of  repairs 
and  necessitates  a  higher  grade  of  skilled  oversight  and  attendance 
which  more  than  compensates  for  the  fuel  economy  acquired.  It 


PARKE:     BRAKING   HIGH-SPEED   TRAINS.  317 

is  not  fuel  economy,  but  it  is  commercial  economy  of  operation, 
which  defines  the  limit  of  such  refinement  and  establishes  a  duty 
which  may  not  be  exceeded  with  commercial  advantage.  Similarly, 
the  extension  of  multiple-control  systems  to  the  application  of 
motors  to  more  than  a  certain  limited  proportion  of  the  axles  upon 
a  train  may  easily  be  attained  by  an  ultimate  cost  whereby 
economy  of  operation  is  impaired. 

The  pertinence  of  the  foregoing  observation  lies  merely  in  the 
fact  that,  while  the  application  of  multiple-control  systems  has, 
in  some  cases,  apparently  been  pushed  to  extremes,  in  an  effort  to 
improve  electrical  train  service,  by  attaining  the  very  highest  ac- 
celeration at  the  sacrifice  of  commercial  economy,  the  absence  of 
any  effort  to  attain  a  fuller  measure  of  the  possible  rate  of  retarda- 
tion, in  stopping,  is  the  more  noteworthy.  That  materially  in- 
creased stopping  efficiency  may  with  propriety  be  employed  in 
high-speed  train  service,  it  is  the  purpose  of  this  paper  to  demon- 
strate; and,  as  every  start,  requiring  high  acceleration,  is  neces- 
sarily attended  by  a  corresponding  stop,  in  which  a  higher  rate  of 
retardation  correspondingly  improves  the  character  of  the  train 
service,  it  is  obvious  that,  if  increased  expense  is  justified  in  mod- 
erately increasing  the  rate  of  acceleration,  materially  increased 
stopping  efficiency,  at  a  comparatively  small  cost,  is  entitled  to 
careful  consideration. 

To  those  who  are  familiar  with  the  results  of  experiments  with 
the  friction  of  brake-shoes  upon  car-wheels  and  the  difference  in 
the  conditions  of  brake  application  at  high  speed  from  those  at  low 
speed,  the  proposal  to  increase  the  force  of  application  of  the  brake- 
shoes  upon  the  wheels  at  high  speeds  will  excite  no  comment. 

The  various  trustworthy  experiments  upon  brako-shoe  friction 
have  uniformly  demonstrated  a  declining  ratio  of  the  friction  to 
the  pressure  of  the  shoe  upon  the  wheel  at  increased  speeds.  For 
the  same  brake-shoe  pressure  the  friction  excited  at  a  speed  of  60 
miles  an  hour  is  but  about  one-half  that  which  occurs  when  the 
speed  is  but  20  miles  an  hour.  Other  causes  result  in  a  reduction  of 
the  brake-shoe  friction  during  continued  application  of  the  brakes ; 
and  this  result  combines  with  the  increase  of  the  friction  through 
reduction  of  speed,  during  the  retardation  of  the  train,  to  main- 
tain a  comparatively  uniform,  though  slightly  increasing,  rate  of 
friction  throughout  the  stop,  until  quite  near  its  close.  Thus,  the 
average  rate  of  retardation  of  the  brakes,  when  applied  to  the  wheels 
at  a  speed  of  60  miles  an  hour,  is  about  one-half  of  that  acquired 


318  PARKE:     BRAKING   HIGH-SPEED   TRAINS. 

with  the  same  brake-shoe  pressure  when  the  initial  speed  is  but  20 
miles  an  hour.  It  is  evident,  therefore,  that  the  same  rate  of  re- 
tardation —  which  may  with  entire  propriety  be  employed  at  all 
speeds  —  can  only  be  acquired  by  increased  pressure  of  the  brake- 
shoes  upon  the  wheels,  to  correspond  with  the  reduced  rate  of 
friction  occurring  at  the  higher  speeds. 

Moreover,  an  application  of  the  brakes  which  will  produce  a 
given  rate  of  retardation  at  one  speed,  without  danger  to  the  rolling- 
stock  or  discomfort  to  the  passengers,  may  also  be  applied  at  any 
other  speed  with  no  more  danger  or  discomfort.  The  high-speed 
brake  was  designed  more  particularly  for  use  upon  high-speed 
trains,  and  it  employs  a  considerably  greater  brake-shoe  pressure 
in  emergency  applications  than  that  of  the  ordinary  quick-action 
brake,  to  more  nearly  realize  the  rate  of  retardation  obtained  in  the 
emergency  application  of  the  quick-action  brake  upon  trains  of 
lower  speeds.  At  such  a  high  speed  as  60  miles  an  hour,  however, 
even  the  emergency  application  does  not  develop  greater  brake-shoe 
friction  than  does  a  full  service  application  of  the  quick-action 
brake  at  a  speed  of  20  miles  an  hour.  It  is  true  that  the  service  ap- 
plication is  attended  by  a  comparatively  gradual  application  of  the 
brake-shoe  pressure,  while  the  emergency  application  develops  the 
greater  brake-shoe  pressure  very  quickly;  but  experience  and  ob- 
servation seemed  fully  to  justify  the  conclusion  that  the  reduced 
rate  of  friction  at  the  higher  speeds  would  permit  the  use  of  even 
the  high-speed  brake  without  noticeable  shock  or  disagreeable 
sensation. 

Though  the  conviction  thus  expressed  three  and  one-half  year? 
ago  was  based  upon  observation,  experience  and  knowledge  of  the 
results  of  experiments  upon  brake-shoe  friction,  it  was,  neverthe- 
less, so  far  as  practical  employment  in  train  service  was  concerned, 
a  theoretical  conclusion.  Since  that  time  experiments  in  the  use 
of  the  high-speed  brake  upon  passenger  trains  have  amply  confirmed 
the  writer's  views  upon  this  subject  and  demonstrated  the  absence 
of  disagreeable  effect  as  well  as  the  highly  increased  rate  of  re- 
tardation in  employing  the  emergency  application  of  the  high-speed 
brake  for  stops  in  high-speed  train  service.  The  time  and  distance 
saved  in  such  stops  permit  the  employment  of  the  maximum  speed 
up  to  a  comparatively  short  distance  from  the  stopping  point  and 
cause  the  train  to  be  brought  to  a  quick,  smooth  stop  in  much  less 
than  half  the  time  and  distance  required  for  an  ordinary  service 
stop. 


PARKS:     BRAKING   HIGH-SPEED   TRAINS.  319 

That  the  shortened  running  time  and  increased  efficiency  of  high- 
speed train  service  —  particularly  local  express-train  service  —  by 
the  employment  of  such  higher  rate  of  retardation,  may  be  attained 
at  a  small  fraction  of  the  expense  at  which  a  lesser  improvement  in 
such  efficiency  can  be  obtained  through  the  increased  acceleration 
resulting  from  extending  the  multiple-control  system  from  the  use 
of  motors  upon  one-half  the  cars  in  the  train  to  their  application  to 
all  of  them,  seems  hardly  open  to  doubt.  The  neglect  to  take  ad- 
vantage of  this  higher  rate  of  retardation  would  seem  to  be  attrib- 
utable chiefly  to  the  long-established  doctrine  that  emergency  ap- 
plications must  not  be  employed  for  service  stops,  under  far  dif- 
ferent conditions.  It  is  to  be  understood  that  such  a  doctrine  still 
applies,  with  all  its  force,  to  the  operation  of  passenger  trains  at 
moderate  speed,  as  well  as  to  freight-train  service.  It  is  only  under 
the  special  conditions  of  uniform  operation  at  high  speeds  —  not 
less  than  50  miles  an  hour  —  that  the  recommendation  of  a  most 
powerful  application  of  a  most  powerful  brake,  in  all  stops,  properly 
applies. 

In  addition  to  the  advantage  of  effecting  a  reduction  of  from  50 
to  75  per  cent  in  the  time  and  distance  required  by  a  service  ap- 
plication of  the  brakes,  a  collateral  advantage  of  material  im- 
portance is  the  much  greater  accuracy  of  the  stop.  In  a  stop  by  a 
service  application  of  the  brakes,  the  application  is  affected  by  the 
personal  judgment  of  the  operator,  whereby  an  element  of  uncer- 
tainty is  introduced  which  almost  invariably  requires  a  subsequent 
release  and  a  second  application  of  the  brakes,  in  order  to  bring  the 
train  to  a  stop  within  the  range  of  the  station  platform.  This 
frequently  involves  more  or  less  "  drifting  "  of  the  train,  at  greatly 
reduced  speed,  to  avoid  stopping  short  of  the  station  and  not  in- 
frequently involves  backing  of  the  train  because  of  inaccurate 
judgment  in  the  application  of  the  brakes,  whereby  the  train  runs 
beyond  the  stopping  point.  In  the  use  of  the  emergency  application, 
not  only  is  the  individual  application  of  every  brake  very  much  more 
prompt  and  powerful,  but  the  rate  of  serial  application  from  car  to 
ear  is  almost  instantaneous  and  is  automatically  established  to  the 
exclusion  of  any  influence  of  the  operator's  judgment.  Grade  and 
alignment  of  the  roadway,  of  course,  influence  the  stopping  dis- 
tance ;  but  such  influences  are  readily  determined  for  each  stopping 
point,  and  the  point  at  which  the  motive  power  should  be  shut  off 
and  the  emergency  application  of  the  brakes  should  occur,  may  be 


320  PARKE:     BRAKING   HIGH-SPEED   TRAINS. 

designated  by  a  post  or  other  permanent  signal,  whereby  the  train 
will  be  brought  to  a  stop  at  the  desired  stopping  point. 

In  comparison  with  the  rate  of  acceleration,  in  starting  steam- 
railroad  trains,  the  rate  of  retardation  in  ordinary  service  stops  has 
been  so  high  that  it  is  not  unnatural  that  increased  efficiency  of 
train  service  has  suggested  higher  rates  of  acceleration  in  starting, 
rather  than  improved  retardation  in  stopping;  but  it  should  now 
be  clear  that  a  really  efficient  high-speed  train  service  may  be  ob- 
tained only  by  also  employing  the  maximum  practical  rate  of  re- 
tardation, by  which  so  large  a  reduction  of  the  time  and  distance  of 
stopping  is  counted.  Electric  train  service  furnishes  exceptional 
conditions  for  attaining  the  maximum  retardation,  as  well  as  the 
maximum  rate  of  acceleration  —  though  for  different  reasons. 
Where  trains  are  drawn  by  steam  locomotives  the  conditions  exist- 
ing at  the  locomotive  and  the  variable  load  carried  in  the  tender 
involve  limiting  the  braking  power  so  that  the  retarding  force  is 
considerably  inferior  to  that  realized  upon  the  cars.  Where  elec- 
tricity is  employed  the  motive  power  is  applied  directly  to  the  cars 
themselves  in  such  a  manner  that  the  maximum  braking  efficiency 
may  be  obtained  as  well  upon  motor  as  upon  other  cars,  and  the 
whole  train  is  thus  subject  to  the  maximum  rate  of  retardation. 

While  the  special  conditions  of  high-speed  train  service  permit 
realization  of  the  maximum  obtainable  retardation  in  ordinary  sta- 
tion stops,  it  will  be  understood,  of  course,  that  all  the  ordinary- 
means  of  general  brake  efficiency  are  contemplated  in  connection 
with  the  brake  apparatus.  In  a  paper  presented  to  the  American  In- 
stitute of  Electrical  Engineers,  and  published  in  the  January,  1903, 
volume  of  proceedings,  the  writer  pointed  out  the  more  important 
features  of  the  brake  apparatus  for  attaining  such  high  efficiency. 
They  included  efficient  foundation  brake-gear  automatic  slack  ad- 
juster, to  maintain  the  minimum  piston  stroke  in  the  brake  cylin- 
ders, and  brake  beams  hung  between  the  wheels  and  adapted  to 
regulate  the  brake-shoe  pressure  so  as  to  compensate  for  the  transfer 
of  weight  from  the  rear  to  the  forward  pair  of  wheels  of  each  truck 
during  the  application  of  the  brakes. 

In  addition  to  such  general  considerations  an  exceedingly  im- 
portant element  of  braking  efficiency  is  the  character  of  the  brake- 
shoes  applied  to  the  wheels.  Extensive  experiments  have  demon- 
strated a  very  wide  variation  in  the  frictional  quality  of  brake-shoes 
of  different  materials,  and,  further,  a  marked  difference  in  the 
friction  of  the  same  brake-shoe  upon  wheels  of  different  materials. 


PARKS:     BRAKING   HIGH-SPEED   TRAINS.  321 

It  is,  in  general,  found  that  the  maximum  frictional  resistance 
occurs  in  the  application  of  soft  cast-iron  shoes  to  chilled  cast-iron 
wheels,  and  the  friction-producing  quality  generally  declines  a8 
harder  brake-shoe  materials  are  employed.  It  should  not  be  con- 
cluded, however,  from  this  general  relation  of  the  hardness  of  the 
brake-shoe  materials  to  the  frictional  quality,  that  soft  material 
only  should  be  employed  in  brake-shoes.  Beside  the  cost  of  soft 
brake-shoes,  which  wear  rapidly,  the  trouble  and  expense  of  replace- 
ment, together  with  the  complications  arising  from  rapid  wear,  are 
highly  persuasive  elements  in  favor  of  the  use  of  harder  materials. 
If  the  inferior  frictional  quality  of  the  harder  brake-shoes  is  com- 
pensated by  correspondingly  increased  pressure  of  the  brake-shoes 
upon  the  wheels,  the  operative  objection  to  the  hard  brake-shoe 
practically  disappears.  The  question  is,  to  a  large  extent,  a  com- 
mercial one.  Increased  pressure  upon  the  harder  shoes  involves,  of 
course,  somewhat  increased  wear ;  but  when,  in  each  case,  the  brake- 
shoe  pressure  is  so  adapted  to  its  frictional  quality  that  the  maxi- 
mum retarding  friction  is  acquired,  the  practical  question  resolves 
itself  into  the  relative  cost  of  initial  installation  and  of  subsequent 
maintenance — to  which  must  be  added  due  consideration  of  trouble 
and  annoyance  arising  from  the  necessity  of  frequent  attention. 

Within  the  past  two  or  three  years,  two  different  series  of  ex- 
periments with  the  high-speed  brake  have  furnished  most  inter- 
esting and  important  information  bearing  upon  this  subject.  In 
one  series,  soft  cast-iron  brake-shoes  were  employed  with  chilled 
cast-iron  wheels.  In  the  other  the  "  Diamond  S  "  form  of  brake- 
shoe  (of  hard  cast-iron,  with  steel  inserts)  was  used  with  steel-tired 
wheels.  Otherwise,  the  conditions  were  fairly  comparable,  the 
tests  being  conducted  in  the  same  general  locality.  In  the  case 
where  soft  cast-iron  shoes  were  employed,  the  initial  air-pressure 
in  the  brake-cylinder  was  about  85 J  Ibs.,  which  became  reduced, 
toward  the  end  of  the  stop,  to  60  Ibs.  In  the  tests  with  the  Dia- 
mond S  brake-shoe,  the  initial  air-pressure  on  the  brake-cylinder 
was  also  about  85J  Ibs.,  which,  by  the  use  of  special  high-speed 
reducing  valve?,  became  reduced  to  a  final  minimum  of  from 
about  69  Ibs.,  from  a  speed  of  80  miles  an  hour,  to  about  78  Ibs., 
in  stopping  a  six-oar  train  from  a  speed  of  50  miles  an  hour. 
Moreover,  in  some  instances,  a  brake-cylinder  pressure  of  75  Ibs. 
or  more  occurred  in  applications  of  the  brakes  at  speeds  of  SO 
miles  per  hour  (and  even  less),  without  producing  wheel-sliding 
of  an  injurious  character  or  exceeding  that  which  occurred  with 

ELEC.  RYS. —  21. 


322  PARKE:     BRAKING   HIGH-SPEED   TRAINS. 

the  use  of  the  soft  cast-iron  brake-shoe,  when  the  final  minimum 
air-pressure  in  the  brake-cylinder  was  but  60  Ibs.  The  stopping 
distances  were  phenomenally  short  in  the  tests  with  the  Dia- 
mond S  brake-shoe,  averaging  602  ft.  from  a  speed  of  50  miles 
an  hour,  982  ft.  at  60  miles  an  hour,  and  1334  ft.  at  70  miles  an 
hour  —  the  shortest  authentic  stops  on  record. 

It  is  true  that  these  tests  were  made  in  dry  weather,  and  that 
the  rails  were  more  or  less  affected  by  sand,  in  which  the  soil  of  the 
country  abounded,  and  particles  of  which  were  carried  about  by 
wind.  It  is  very  doubtful  whether  such  high  terminal  brake- 
cylinder  pressure  might  be  safely  employed  even  with  such  hard 
brake-shoes,  under  the  varying  rail  conditions  of  regular  service  — 
the  corresponding  total  brake-slioe  pressures,  as  customarily  cal- 
culated, being  from  104  to  117  per  cent  of  the  weight  of  the  braked 
cars;  but  these  experiments  clearly  illustrate  both  the  fact  that 
wide  difference  in  the  friction al  qualities  of  brake-shoes  should  be 
given  proper  consideration  in  determining  the  brake-shoe  pressure, 
and  also  the  fact  that,  with  a  properly  determined  pressure,  cer- 
tain forms  of  hard  brake-shoes  may  yield  as  good,  or  perhaps  even 
better,  average  retarding  influence  than  soft  cast-iron  brake-shoes. 
It  is  worthy  of  note  that  the  material  in  the  brake-shoes  employed 
in  these  experiments  was  so  hard  that  a  number  of  the  shoes  were 
broken  during  the  tests  —  but  without  apparently  affecting  their 
utility,  inasmuch  as  the  form  of  the  shoes  remained  unchanged, 
the  parts  being  held  in  place  by  a  steel  plate  cast  in  the  outer  sur- 
face of  the  shoe. 

The  foregoing  considerations  assume  the  use  of  the  automatic 
air  brake.  Inasmuch  as  high-speed  trains  have  been  under  con- 
sideration, no  other  form  than  an  automatic  brake  could  properly 
be  considered.  In  the  case  of  a  service  employing  single  cars,  the 
advantage  of  an  automatic  brake  practically  disappears  and  more 
simple  forms  of  apparatus  may  be  employed  to  advantage;  but, 
where  two  OT  more  cars  are  assembled  in  trains,  and  particularly 
in  high-speed  trains,  the  necessity  of  providing  for  the  contingency 
of  train  partings  permits  but  the  one  prudent  and  safe  course  of 
employing  an  automatic  brake,  and,  thus  far,  the  automatic  air 
brake  alone  has  become  safely  established  as  meeting  all  the 
requirements  of  service.  The  necessity  of  the  most  efficient  high- 
speed train  service  requires,  in  addition,  the  most  forcible  appli- 
cation of  the  most  efficient  form  of  automatic  air  brake  —  the 
emergency  application  of  the  "  high-speed  "  brake. 


ALTERNATING-CUBEENT  MOTOKS. 


BY  CHARLES  PROTEUS  STEINMETZ. 

I. 

In  recent  years  a  number  of  types  of  alternating-current  motors 
have  become  of  interest,  which,  while  not  new  in  their  general 
principles,  but  antedating  even  the  polyphase  induction  motor. 
have  been  for  some  time  overshadowed  by  the  latter,  due  to  its 
greater  simplicity,  resulting  from  the  absence  of  the  commutator, 
and  its  constancy  of  speed. 

With  the  rapid  extension  of  the  applications  of  electricity, 
alternating-current  motors  were  demanded  for  railway  and  similar 
classes  of  work,  which  give  high-starting  torque  efficiency  and 
high  efficiency  over  a  wide  range  of  speed;  that  is  a  speed-torque 
characteristic  similar  to  that  of  the  direct-current  series  motor. 
The  characteristic  of  the  alternating-current  induction  motor, 
however,  is  that  of  a  constant-speed  motor,  and  indeed  the  poly- 
phase induction  motor  can  theoretically  be  considered  as  an  adapta- 
tion of  the  direct-current  shunt  motor  to  alternating  current,  as 
I  have  shown  elsewhere.  By  the  introduction  of  the  commutator 
almost  any  speed-torque  characteristic  can  be  produced.  A  number 
of  types  of  such  commutator  motors  have  been  produced  and  more 
or  less  developed,  but  thus  far  practical  experience  has  not  yet 
advanced  so  far  as  to  weed  out  the  less  desirable  types.  To  enable 
a,  critical  judgment  of  their  relative  advantages  a'nd  disadvantages, 
I  shall  endeavor  in  the  following  to  give  a  general  theory  of  the 
alternating-current  motor,  applicable  alike  to  the  induction  and 
commutator  motors. 

The  starting  point  of  the  theory  of  the  polyphase  and  single- 
phase  induction  motor  usually  is  the  general  alternating-current 
transformer,  and  from  the  equations  of  the  general  alternating- 
current  transformer  the  induction  motor  equations  can  be  de- 
veloped.1 Coming,  however,  to  the  commutator  motors,  this 
method  becomes  less  suitable. 

1.  Transactions  A.  I.  E.  E.,  1895. 

[323] 


224  8TEINMETZ:     ALTERNATING-CURRENT  MOTORS. 

In  its  general  form  the  alternating-current  motor  consists  of 
one  or  more  stationary  electric  circuits  magnetically  related  to  one 
or  more  rotating  electric  circuits.  These  circuits  can  be  excited 
by  alternating  currents,  or  some  by  alternating,  others  by  direct 
current,  or  closed  upon  themselves,  etc.,  and  connection  can  be 
made  to  the  rotating  member  either  by  collector  rings  —  that  is,  to 
fixed  points  of  the  windings  —  or  by  commutator  —  that  is  to  fixed 
points  in  space. 

The  alternating-current  motors  can  be  subdivided  into  two 
classes  —  those  in  which  the  electric  and  magnetic  relations  be- 
tween stationary  and  moving  members  do  not  vary  with  their 
relative  positions,  and  those  in  which  they  vary  with  the  relative 
positions  of  stator  and  rotor.  In  the  latter  a  cycle  of  rotation 
exists,  and  therefrom  the  tendency  of  the  motor  results  to  lock  at 
a  speed  giving  a  definite  ratio  between  the  frequency  of  rotation 
and  the  frequency  of  impressed  e.m.f.  Such  motors,  therefore, 
are  synchronous  motors. 

The  main  types  of  synchronous  motors  are  as  follows: 

(1)  One  member  supplied  with  alternating  and  the  other  with 
direct  current  —  polyphase  or  single-phase  synchronous  motors. 

(2)  One  member  excited  by  alternating  current,  the  other  con- 
taining a  single  circuit  closed  upon  itself  —  synchronous  induction 
motors. 

(3)  One  member  excited  by  alternating  current,  the  other  of 
different  magnetic  reluctance  in  different  directions  (as  polar  con- 
struction) —  reaction  motors. 

(4)  One  member  excited  by  alternating  current,  the  other  by 
alternating  current  of  different  frequency  or  different  direction  of 
rotation  —  general   alternating-current   transformer   or   frequency 
converter. 

No.  1  is  the  synchronous  motor  of  the  electrical  industry.  Nos. 
2  and  3  are  used  occasionally  to  produce  synchronous  rotation  with- 
out direct-current  excitation,  and  of  very  great  steadiness  of  the 
rate  of  rotation,  where  weight  —  efficiency  and  power  factor  are  of 
secondary  importance.  No.  4  is  used  to  some  extent  as  frequency 
converter. 

In  the  following  I  shall  discuss  only  that  type  of  motor  in  which 
the  electric  and  magnetic  relations  between  the  stator  and  rotor 
do  not  vary  with  their  relative  positions,  and  the  torque  is,  there- 


STEIN METZ:     ALTERNATING-CURRENT  MOTORS.  32-> 

fore,  not  limited  to  a  definite  synchronous  speed.  This  requires 
that  the  rotor  when  connected  to  the  outside  circuit  is  connected 
through  a  commutator,  and  when  closed  upon  itself  several  closed 
circuits  exist,  displaced  in  position  from  each  other  so  as  to  offer 
a  resultant  closed  circuit  in  any  direction.  In  the  theoretical  in- 
vestigation I  shall  use  the  method  of  complex  quantities,  the  ap- 
plication of  which  to  alternating-current  phenomena  I  outlined  in 
a  paper  before  a  previous  congress.2  The  extension  of  this  method 
to  vector  products  as  torque  and  power  is  given  in  the  appendix.* 

II. 

An  alternating  current  /  flowing  through  an  electric  circuit 
produces  a  magnetic  flux  $  interlinked  with  this  circuit.  Consider- 
ing equivalent  sine  waves  of  7  and  0, 0  lags  behind  I  by  the  angle 
of  hysteretic  lag  a.  This  magnetic  flux  </>  induces  an  e.m.f.  E=s 
2  TT  Nn&,  where  N  =  f requenc}',  n  =  number  of  turns  of  electric 
circuit.  This  induced  e.m.f.  E  lags  90  deg.  behind  the  magnetic 
flux  $,  hence  consumes  an  e.m.f.  90  deg.  ahead  of  0,  or  90  —  «  deg. 
ahead  of  7.  This  may  be  resolved  in  a  wattless  component:  E  = 
2  -IT  Nn  $  cos  a  =2  IT  N  L  I  =  x  I,  the  e.m.f .  consumed  by  self- 
induction,  and  an  energy  component :  E"  =  2  TT  Nn  &  sin  a=  2  tr 
N  H  I  =  r"  I  =  e.m.f.  consumed  by  hysteresis  (eddy  currents, 
etc.),  and  is,  therefore,  in  vector  representation  denoted  by 

E'  =  ~jxl  and  E"=r"  I 

where  x  =  2  TT  N  L  —  reactance,  L  =  inductance, 

r"  =  effective  hysteretic  resistance. 

The  ohmic  resistance  of  the  circuit,  r',  consumes  an  e.m.f.  // 
in  phase  with  the  current,  and  the  total  or  effective  resistance  of 
the  circuit  is,  therefore,  r  =  r'  +  r",  and  the  total  e.m.f.  consumed 
by  the  circuit,  or  the  impressed  e.m.f.  is 

E=(r  — jx)  I  =  Z1 
where 

Z  =  r  —  jx  =  impedance,  in  vector  notation, 

z  =  V?*2  +  z2  =  impedance,  in  absolute  terms. 

If  an  electric  circuit  is  in  inductive  relation  to  another  electric 
circuit,  it  is  advisable  to  separate  the  inductance  L  of  the  circuit 
into  two  parts — the  self-inductance  S,  which  refers  to  that  part  of 

2.  Chicago,  1903,  Proceedings  Int.  Elec.  Cong.,  1894. 

3.  See  also  Transactions  A.  I.  E.  E.,  1899 


326  STEIN METZ:     ALTERNATING-CURRENT  MOTORS. 

the  magnetic  flux  produced  by  the  current  in  one  circuit  which  is 
interlinked  only  with  this  circuit  but  not  with  the  other  circuit, 
and  the  mutual  inductance,  M.,  which  refers  to  that  part  of  the 
magnetic  flux  interlinked  also  with  the  second  circuit.  The 
desirability  of  this  separation  results  from  the  different  character 
of  the  two  components:  The  self -inductance  induces  a  wattless 
e.m.f.  and  thereby  causes  a  lag  of  the  current,  while  the  mutual 
inductance  transfers  power  into  the  second  circuit,  hence  generally 
does  the  useful  work  of  the  apparatus.  This  leads  to  the  distinc- 
tion between  the  self-inductive  impedance  Z0  =  r0  —  j  XQ  and  the 
mutual  inductive  impedance  Z  =  r  —  j  x. 

r0  is  the  coefficient  of  power  consumption  by  ohmic  resistance, 
hysteresis  and  eddy  currents  of  the  self -inductive  flux  —  effective 
resistance. 

x0  is  the  coefficient  of  e.m.f.  consumed  by  the  self-inductive 
flux  —  self-inductive  reactance. 

r  is  the  coefficient  of  power  consumption  by  hysteresis  and  eddy 
currents  due  to  the  mutual  magnetic  flux  (hence  contains  no 
ohmic  resistance  component). 

x  is  the  coefficient  of  e.m.f.  consumed  by  the  mutual  magnetic 
flux. 

The  e.m.f.  consumed  by  the  circuit  is  then 
E  =  Z0  I  +  Z  I 

If  one  of  the  circuits  rotates  relatively  to  the  other,  then  in 
addition  to  the  e.m.f.  of  self -inductive  impedance:  ZQ  I  and  the 
e.m.f .  of  mutual-inductive  impedance  or  e.m.f.  of  alternation :  Z  I, 
an  e.m.f.  is  consumed  by  rotation.  This  e.m.f.  is  in  phase  with 
the  flux  through  which  the  coil  rotates  —  that  is  the  flux  parallel 
to  the  plane  of  the  coil  —  and  proportional  to  the  speed  —  that  is 
the  frequency  of  rotation  —  while  the  e.m.f.  of  alternation  is  90 
deg.  ahead  of  the  flux  alternating  through  the  coil  —  that  is  the 
flux  parallel  to  the  axis  of  the  coil  —  and  proportional  to  the  fre- 
quency. If,  therefore,  Z'  is  the  impedance  corresponding  to  the 
former  flux,  the  e.m.f.  of  rotation  is  /  a  Zr  I,  where  a  is  the  ratio 
of  frequency  of  rotation  to  frequency  of  alternation,  or  the  speed 
expressed  as  a  fraction  of  synchronous  speed.  The  total  e.m.f.  con- 
sumed in  the  circuit  is  thus :  E=Z0I-}-ZI-}-jaZ'L 

Applying  now  these   considerations  to   the   alternating-current 

motor,  we  assume  all  circuits  reduced  to  the  same  number  of  turns 

-  that  is,  selecting  one  circuit,  of  n  effective  turns,  as  starting 


STEIN METZ:     ALTERNATING-CURRENT  MOTORS.  327 

point,  if  HI  =  number  of  effective  turns  of  any  other  circuit,  all 
the  e.m.f  s.  of  the  latter  circuit  are  divided,  the  currents  multi- 
plied with  the  ratio  njn,  the  impedances  divided,  the  admittances 
multiplied  with  (n^/n)2  This  reduction  of  the  constants  of  all 
circuits  to  the  same  number  of  effective  turns  is  convenient  by 
eliminating  constant  factors  from  the  equations,  and  so  permitting 
a  direct  comparison.  When  speaking,  therefore,  in  the  following 
of  the  impedance,  etc.,  of  the  different  circuits,  we  always  refer  to 
their  reduced  values  (as  it  is  customary  in  induction  motor  design- 
ing practice) . 

Let  then,  in  Fig.  1,  E0f  70,  Z0  =  impressed  e.m.f.,  current  and 
self-inductive  impedance  resp.  of  a  stationary  circuit,  E^  1^  Z^= 


FIG.  i. 

impressed  e.m.f.,  current  and  inductive  impedance  respectively  of  a 
rotating  circuit,  w  =  angle  between  the  axis  of  the  two  circuits, 
Z  =  mutual-inductive  or  "  exciting  "  impedance  in  the  direction 
of  the  axis  of  the  stationary  coil,  Zr  =  exciting  impedance  in  the 
direction  of  the  axis  of  the  rotating  coil,  Z"  =  exciting  impedance 
at  right  angles  to  the  latter  axis,  and  a  =  speed,  as  fraction  of  syn- 
chronism. It  is  then: 
In  the  stationary  coil: 

E.m.f.  consumed  by  self-inductive  impedance:  Z0  70 
E.m.f.  consumed  by  mutual-inductive  impedance:  Z    (/„  +  /! 
cos  w)  since  the  m.m.f.  acting  in  the  direction  of  the  axis  of  the 
stationary  coil  is  the  resultant  of  both  currents.    Hence : 

Eo  =  Z0I0  +  Z  (Zo+7,  cos*) 
In  the  rotating  circuit,  it  is : 

E.m.f.  consumed  by  self-inductive  impedance:   Zl  J4 
E.m.f.  consumed  by  mutual-inductive  impedance  or  "e.m.f.  of 
alteration:"  Z'  (II  +  70  cos  «>) 


328  STEIN  METZ:     ALTERNATING-CURRENT  MOTORS.  > 

E.m.f.  of  rotation:  jaZ"  70  sin  «> 

Hence  the  impressed  e.rn.f.  : 

E1=Z1  7±  +  Z'  (71  +  70  cos  «)  +   ;  aZ"  70  sin  « 

In  a  structure  with  uniformly  distributed  winding,  as  used  in 
induction  motors,  repulsion  motors,  etc.,  Z1  =  Z"  =  -Zt  that  is,  the 
exciting  impedance  is  the  same  in  all  directions. 

Z  is  the  reciprocal  of  the  "  exciting  admittance,"  Y  of  the  in- 
duction motor  theory. 

In  the  most  general  case,  of  a  motor  containing  n  circuits,  of 
which  some  are  revolving,  some  stationary,  if: 

miu  /kj  Zk  =  impressed  e.m.f.,  current  and  self  -inductive  im- 
pedance respectively  of  any  circuit  Tc 

Z1,  and  Zli  =  exciting  impedance  parallel  and  at  right  angles 
respectively  to  the  axis  of  a  circuit  if 

«>i  =  angle  between  the  axes  of  coils  k  and  if  and 

fl  =  speed,  as  fraction  of  synchronism,  or  "  frequency  of  rota- 
tion." 

It  is  then,  in  a  coil  i: 


EI  =  Zi  /i  +  Z!  >    ^k  cos 

i  i 

where  : 
Zi  Ii   =  e.m.f.  of  self  -inductive  impedance. 

n_ 

Z1  yK  7k  cos  oi  =^.  e.m.f.  of  alternation 

E[=jaZ"  >F  7k  sin  w*,   ==  e.m.f.  of  rotation 

which  latter  =  o  in  a  stationary  coil,  in  which  a  =  o. 

The  power  output  of  the  motor  is  the  sum  of  the  powers  of  all 
the  e.m.f  s.  of  rotation,  hence,  in  vector  denotation4: 


=  «  X  /  jZil  XL  /k  Sin  a;,*  ,  /|  /» 
and,  therefore,  the  torque,  in  synchronous  watts8: 


4.  See  appendix.    Also  Transactions  A.  I.  E.  E.,  1899. 

5.  See  Transactions  A.  I.  E.  E.,  1897,  1898,  1900. 


STEINMETZ:     ALTERNATING-CURRENT  MOTORS.  329 

The  power  input,  in  vector  denotation,  is: 


=  jr/  jsi. 


and  therefore  : 
P0J  =  true  power  input 

P0*  =  wattless  voltampere  input 

Qo  =  V(P0l)z  +  (P03)2  =  apparent  or  voltampere  input 

P  7* 

p-y  =  efficiency  ;  -p-f  torque  efficiency  ; 

•*o  •*  o 

P  T7 

—  -  =  apparent  efficiency;  -75—  =  apparent  torque  efficiency 

Vo  Vo 

p  1 

-~-  =  power  factor 

^o 

From  the  n  circuits  :  i  =  1,  2,  .  .  .  thus  result  n  linear  equa- 
tions, with  2n  complex  variables:  Ii  and  E{. 

Hence  n  further  conditions  must  be  given  to  determine  th-3 
variables.  These  obviously  are  the  conditions  of  operation  of  the 
n  circuits. 

Impressed  e.m.fs.  Ei  may  be  given. 

Or  circuits  closed  upon  themselves:  Ei=o. 

Or  circuits  connected  in  parallel  :  GI  E\  =  ck  E^f  where  ci  and  ck 
are  the  reduction  factors  of  the  circuits  to  equal  number  of  ef- 
fective turns,  as  discussed  before. 

Or  circuits  connected  in  series:  c\  1\  =  ck/k>  etc. 

When  a  rotating  circuit  is  connected  through  a  commutator,  the 
frequency  of  the  current  in  this  circuit  obviously  is  the  same  a? 
the  impressed  frequency.  Where,  however,  a  rotating  circuit  is 
permanently  closed  upon  itself,  its  frequency  may  differ  from  the 
impressed  frequency,  as,  for  instance,  in  the  polyphase  induction 
motor  it  is  the  frequency  of  slip  s  =  l  —  a.  and  the  self  -inductive 
reactance  of  the  circuit,  therefore,  is:  5  x,  though  in  its  reaction 
upon  the  stationary  system  the  rotating  system  necessarily  is  al- 
ways of  full  frequency. 

After  this  introduction  we  come  now  to  the  discussion  of  a  few 
motor  types.  We  shall,  however,  consider  only  such  types  as  have 
been  more  or  less  developed  commercially  or  at  least  seriously  con- 
sidered. 


330  STEIN METZ:     ALTERNATING-CURRENT  MOTORS. 

III. 

(1)   Polyphase  Induction  Motor. 

In  the  polyphase  induction  motor  a  number  of  primary  circuits, 
displaced  in  position  from  each  other,  are  excited  by  polyphase 
e.m.f's.  displaced  in  phase  from  each  other  by  a  phase  angle 
equal  to  the  position  angle  of  the  coils.  A  number  of  secondary 
circuits  are  closed  upon  themselves.  The  primary  usually  is  ttw 
stator,  the  secondary  the  rotor. 

In  this  case  the  secondary  system  always  offers  a  resultant 
closed  circuit  in  the  direction  of  the  axis  of  each  primary  coil,  ir- 
respective of  its  position. 

Let  us  assume  two  primary  circuits  in  quadrature  as  simplest 
form,  and  the  secondary  system  reduced  to  the  same  number  of 
phases  and  the  same  number  of  turns  per  phase  as  the  primary 
system.  With  three  or  more  primary  phases  the  method  of  pro- 
cedure and  the  resultant  equations  are  essentially  the  same. 


k 
FIG.  2. —  POLYPHASE  INDUCTION  MOTOB. 

Let  in  the  motor  shown  diagrammatically  in  Fig.  2 : 

E '    and  jE     I  and  //   .  Z    =  impressed  e.m.f's.,  currents  and 

•"OJO  •      O  O 

self-inductive  impedance  respectively  of  the  primary  system. 

o,  Zj  and  jllf  Z^  =  impressed  e.m.f .,  currents  and  self-inductive 
impedance  respectively  of  secondary  system,  reduced  to  primary. 

Z  =  mutual-inductive  impedance  between  primary  and  sec- 
ondary. 

a  =  speed ;  s  =  1  —  a  =  slip,  as  fraction  of  synchronism. 

The  equation  of  the  primary  circuit  is  then : 

(/„-',)  (i) 


OF  • 

UNIVERSITY 

x/ 

STEIN  METZ:     ALTERNATING-CURRENT  MOTORS.  331 

The  equation  of  the  secondary  circuit: 

o  =  ZJi+Z  (I-  1,  )  +jaZ  (jlf-  ]'I0)  (2) 

from  (2)  follows: 

Z0(l-a)        _  Zs 

7l        o          -  /0  ZtZ 


and,  substituted  in  (1)  : 
Primary  current: 

T         ™  Zs+Zj  _  ^  ... 

2o-  ^o  ZZ0s+ZZl+Z0Zl  v   ; 

Secondary  current  : 


Exciting  current: 

9 

I=I  —  7i=  Eo 


E.m.f.  of  rotation: 

jl0)=aZ  C 

zz, 


=  aE. 


It  is,  at  synchronism:    s  =  o: 

T       E«        T        .r-T-w- 

/0  =^FC;  "       '  ~ 

At  standstill  :      s  =  1  ; 


„ 

" 


Introducing  as  parameter  the  counter  e.m.f.,  or  e.m.f.  of  mutual 
induction: 


or: 


it  is,  substituted: 
Counter  e.m.f  .  : 


hence  : 

Primary  impressed  e.m.f.: 

YO\ 


^        + 
ZZi      ~Zi+Z  l    } 


332  STEIN  HETZ:     ALTERNATING-CURRENT  MOTORS. 

E.m.f.  of  rotation: 

E^=Ea  =  E  (1—8).  (10) 

Secondary  current: 


Primary  current: 
Exciting  current: 


These  are  the  equations  from  which  the  transformer  theory  of 
the  polyphase  induction  motor  starts. 

Since  the  frequency  of  the  secondary  induced  currents  is  the 
frequency  of  slip,  hence  varies  with  the  speed  a  =  1  —  5.  the  sec- 
ondary self  -inductive  reactance  also  varies  with  the  speed,  and  so 
the  impedance: 

Z1  =  r1  —  jsx1  (14) 

The  power  output  of  the  motor,  per  circuit,  is: 

e02z2«(l—  3)          /,.*_»  /i-x 

(fl+}SXl) 


where  the  brackets  []  denote  the  absolute  value  of  the  term  in- 
cluded by  it,  and  the  small  letters  e0,  z,  etc.,  the  absolute  values 
of  the  vectors  E  o  ,  Z,  etc. 

Since  the  imaginary  term  of  power  seems  to  have  no  physical 
meaning,  it  is: 
Mechanical  power  output: 

P- 

~ 

This  is  the  power  output  at  the  armature  conductors,  hence  includes 
friction  and  windage. 

The  torque  of  the  motor  is: 

x,  «•__          ( 

V    ; 


i  ]2 

The  imaginary  component  of  torque  seems  to  represent  the  ra- 
dial force  or  trust  acting  between  stator  and  motor.  Omitting  it, 
it  is: 


STEIN METZ:     ALTERNATING-CURRENT  MOTORS.  333 

The  power  input  of  the  motor  per  circuit  is: 
P      /E     I  / 


°.  y7  77 

ZZ0fi  -{-  ZZV  -f-  Zo%1 

=  PJ+jPo* 

where:     PJ  =  true   power,    P\=  reactive   or   "wattless   power," 

QQ  =  \/  p?  4-  pi2  =  apparent  power,  or  voltampere  input 

o  o 

Herefrom  follows  power  factor,  efficiency,  etc. 

Introducing  the  parameter:    E,  or  absolute:  et  it  is: 
Power  output: 


(80) 

O 

Power  input: 


2  ,ZZ0.9  +  ZZ,         p  ^-_i 

zz,  ' 


9/0  , 

!>  ~ 


And  since:     -1  =  a  +  *  r,  =  2Q  +  r,,  and  ifari  =  P,  it  is: 


^o  =  ft,  ^o  +  «i2n  +  C2  r  +  P)  +  j(i<?  X0  +  n2  ^  +  ^  a;)  (21) 

Where: 

i02  r0=  primary  resistance  loss, 
i^r^=  secondary  resistance  loss, 
i002r=core  loss   (and  eddy  current  loss), 

P  r=:  OUtpUt, 

^o2  a*o=  primary  reactive  voltampcres, 


334  STEINMETZ:     ALTERNATING-CURRENT  MOTORS. 


=  secondary  reactive  voltamperes, 
t002  x  =  magnetizing  voltamperes. 
Introducing  into  the  equations  (3)  (4)  (5)  (6)  (8)  the  terms: 


Where  JL0  and  ^  are  small  quantities,  and  :   *  =•  ^Q  +  ^  is  the 
"  characteristic  constant  "  of  the  induction  motor  theory,  it  is  : 
Primary  current: 

•r  _  -ffi)  s  4"  ^i  -^o      8  4- 

" 


Z      «*o  +   *l   +   Vl  Z      'I*  +h 

Secondary  current: 

/-^o  s  __  E«         8  (24) 

Z      ^0  +  *i  +  Vi  ~  Z    sA0  +  ^ 

Exciting  current  : 


T        _     -0 

~ 


Z 
E.m.f  .  of  rotation  : 


a   .     ,    f1   ,     .  ,  =  E0  a    .   ^      -  (26) 


Counter  e.m.f  .  : 


=  ^  (27) 


As  instance  are  shown,  in  Fig.  3,  with  the  speed  as  abscissae,  the 
curves  of  a  polyphase  induction  motor  of  the  constants: 

e0=  320  volts, 
*  Z  =  1  —  10;  ohms, 

Z0=Zi=.l  —  .3;  ohms 
hence  :     A0=  ^=  .0307  +  .0069;. 

It  is: 


320  j  10.30s  +(s  +  .!).;} 
1.635)  +J(. 
2048  (1—  s) 


. 
(1.03  +  1.635)  +J(.H  —  5.99s) 


(l  —  5)T 

«+.!  „         .11—6.99* 

tan  o)'=  —3—;  tan    " 


10.3s'  1.03+1.63* 

cos  (a?—  co)=  power  factor. 

The  curves  show  the  well-known  characteristics  of  tbe  polyphase 
induction  motor :  approximate  constancy  of  speed  at  all  loads,  and 
good  efficiency  and  power  factor  within  this  narrow  speed  range, 
but  poor  constants  at  all  other  speeds. 


STEIN METZ:     ALTERNATING-CURRENT  MOTORS. 


337) 


(2)    Single-Phase  Induction  Motor. 

In  the  single-phase  induction  motor  one  primary  circuit  acts 
upon  a  system  of  closed  secondary  circuits  which  are  displaced 
from  each  other  in  position  on  the  secondary  member. 

Let  the  secondary  be  assumed  as  two-phase,  that  is  containing 
or  reduced  to  two  circuits  closed  upon  themselves  at  right  angles 
to  each  other.  While  it  then  offers  a  resultant  closed  secondary 
circuit  to  the  primary  circuit  in  any  position,  the  electrical  dis- 
position of  the  secondary  is  not  symmetrical,  but  the  directions 
parallel  with  the  primary  circuit  and  at  right  angles  thereto  are  to 


1.0 


Fia.  3. 


be  distinguished.  The  former  may  be  called  the  secondary  energy 
circuit,  the  latter  the  secondary  magnetizing  circuit,  since  in  the 
former  direction  power  is  transferred  from  the  primary  to  the 
secondary  circuit,  while  in  the  latter  direction  the  secondary  cir- 
cuit can  act  magnetizing  only. 

Let,  in  the  diagram  Fig.  4: 

E0,  I0,  Z0  =  impressed  e.m.f.,  current  and  self-inductive  im- 
pedance respectively  of  the  primary  circuit 

/1?  Z^  =  current  and  self-inductive  impedance  respectively  of 
the  secondary  energy  circuit 

72J  Z±  =  current  and  self-inductive  impedance  respectively  of 
the  secondary  magnetizing  circuit 


336  STEIN  METZ:     ALTERNATING-CURRENT  MOTORS. 

Z  =  mutual-inductive  impedance 

md  let:    S0  =  1  —  a*  (where  s0  is  not  the  slip) 


FIG.  4L  —  SINGLE-PHASE  INDUCTION  MOTOR. 


It  is  then  : 
Primary  circuit: 

E*  =  Z0Io  +  Z  Co  —  'i) 
Secondary  energy  circuit  : 

o  =  ZJi  +  Z  (A  —  /0)  +jaZ  I, 
Secondary  magnetizing  circuit: 

o  =  Z1l,  +  Z  1,  +  jaZ  (/„-/») 
hence  : 

r  _    r      Z 
° 


and,  substituted: 
Primary  current: 


ZZi 


Secondary  energy  current: 


Secondary  magnetizing  current: 


E.m.f.  of  rotation  of  secondary  energy  circuit: 


E.mf.  of  rotation  of  secondary  magnetizing  circuit: 
E*=jaZ  (I.-I^^jaE.22^^ 

where  : 
-#  =  Zo  (Z2  so  -I-  2  ZZi  +  Zi2)  +  ZZi  (Z  +  ZJ 


(1) 
(2) 
(3) 


/R. 

(6) 


(8) 
(9) 

(10) 
(11  ) 


STEINMETZ:     ALTERNATING-CURRENT  MOTORS. 
It  is,  at  synchronism :   a  —  1,  s0=  o 

T  7^  *    >5  "T"    ^1 


7      =__'    E       Z. 

777    1 77T 

^i  =  ^o    , 


Hence,  at  synchronism,  the  secondary  current  of  the  single-phase 
induction  motor  does  not  become  zero,  as  in  the  polyphase  motor, 
but  both  components  of  secondary  current  become  equaL 

At  standstill :  a  =  o,  s0  =  1  it  is : 

2       jg   Z  +  Z\ 

ZZo  ~\~  ZZi  +  Zo  Zi 


Z,Zo  ~h  ZZi  -\-  Zo  Zi 

That  is,  primary  and  secondaiy  current  corresponding  thereto  have 
the  same  values  as  in  the  polyphase  induction  motor,  page  8. 
This  was  to  be  expected. 

Introducing  as  parameter  the  counter  e.m.f.  or  e.m.f.  of  mutual 
induction : 

T/T  TjJ  F7        ~T 

&  =^o — ^o  1o 

and  substituting  for  I0  from  (6),  it  is: 
Primary  impressed  e.m.f. : 

*7    ( *7^    o      I    o    ^7  ?7      i     ?7  2\     i     ?7 17 

Primary  current: 


Secondary  energy  circuit: 


--P         o  _    o  a'E 

»=   '  ~~  ~ 


Secondary  magnetizing  circuit: 

n    T?. 

r  06) 


ELEC.  RYS. —  22. 


33S  8TEIXMETZ:     ALTERNATING-CURRENT  MOTORS. 

E2*  =  jaE  (17) 

And: 

/o-A=f  (18) 

These  equations  differ  from  the  equations  of  the  polyphase  in- 
duction motor  by  containing  the  term:  s0=  (1  —  a2)  instead  of: 

s=(l  —  a),  and  by  the  appearance  of  the  terms:—!?  -  and: 

2    Tji 

-  .   »,  ,  of  frequency  (1  +  a),  in  the  secondary  circuit. 
Z  ~r  Z\ 

The  power  output  of  the  motor  is  : 


_o»«0'  a?  rt  («.  z2  -  z,  »)  (19) 

[Up 

and  the  torque,  in  synchronous  watts  : 

-o  (20) 

From  these  equations  it  follows  that  at  sjrnchronism  torque  and 
power  of  the  single-phase  induction  motor  are  already  negative. 
Torque  and  power  become  zero  for: 


hence:  «  : 

that  is,  very  slightly  below  synchronism :    Let  z  =  10,  z±  =  A 
it  is:     a  =  .9995. 

In  the  single-phase  induction  motor,  the  torque  contains  the  speed 
a  as  factor,  and  thus  becomes  zero  at  standstill. 

Neglecting  quantities  of  secondary  order,  it  is,  approximately: 

T  -  F               Z*o+*Zi  |Mx 

20  =  ±LQ  ^,  ^.  (22) 

/i  =  ^0    ^(^^°^  +  2^0^  (23) 

72  =  -> ^0  z(Zo*>+ZZi)+*ZoZi          (24) 

js',1  =  «2  ^;  z(Zo*o-\^zZi)  +  *ZoZi        (25) 

^   =>    ^     V   .  V     .       i    ^'     L    o   ^     V  <26> 


STEIN METZ:     ALTERNATING-CURRENT  MOTORS. 


339 


This  theory  of  the  single-phase  induction  motor  differs  from 
that  previously  communicated  (see  note  1,  ante),  in  that  it  repre- 
sents more  exactly  the  phenomena  at  intermediate  speeds,  which 
are  only  approximated  in  the  transformer  theory  of  the  single- 
phase  induction  motor. 

As  instance  are  shown,  in  Fig.  5,  with  the  speed  as  abscissae,  the 
curves  of  a  single-phase  induction  motor,  of  the  constants: 
e0  =  400  volts 
Z  =  1  —  10;  ohms 
Zo  ^^  Z1=.'L  — .3;  ohms 
hence : 

/0  =  400  -p-  amps. 

N  =  (s  +.2)—  ;(10s  +.6—  .60) 


T '  = 


1616  as 


120 
JIG 
100 
90 
80 
TO 
60 
50 
40 
80 
20 
10 


SINGLE  PHASE 

INDUCTION  MOT08 

400  VOLTS 


~850— 


-250- 
-200- 


-50- 


t 
100 

90 
80 
TO 
60 
60 
40 
80 
20 
10 


Pro.  5. 

(3)   Single-phase  Condenser  Motor. 

The    single-phase    induction    motor    is    not    self -starting,    as 
seen    from    the    equations    and    diagram,    Fig.    5.      To    secure 


340 


STEIN METZ:     ALTERNATING-CURRENT  MOTORS. 


starting  torque,  either  a  commutator  has  to  be  used  —  that 
is,  the  motor  started  as  repulsion  motor  or  series  motor,  etc. 
—  or  a  quadrature  magnetic  flux  impressed  upon  the  motor,  that 
is  the  motor  converted  into  a  more  or  less  unsymmetrical,  poly- 
phase motor.  To  a  considerable  extent  used  in  practice  are  only 
the  starting  as  repulsion  motor,  which  will  be  discussed  later,  and 
the  starting  by  a  condenser  in  the  tertiary  circuit,  both  methods 
giving  good  starting  efficiencies.  The  use  of  a  condenser  also  per- 
mits to  greatly  increase  the  power  factor  in  running,  by  retaining 
the  condenser  in  circuit.  This  is  usually  carried  out  by  employing 
a  three-phase  winding  on  the  motor  primary,  of  which  two  ter- 
minals are  connected  to  the  single-phase  supply,  two  terminals 
permanently  connected  to  a  condenser,  either  directly  or  by  step- 


"t JJL 

Fro.  6. —  INDUCTION   SINGLE-PHASE   CONDENSEB   MOTOR. 

up  transformer.  This  condenser  so  closes  a  circuit  displaced  by  60 
deg.  in  position  from  the  primary  circuit,  as  shown  diagrammati- 
cally  in  Fig.  6. 

Let,  in  the  diagram  Fig.  6,  of  such  a  single-phase  condenser 
motor : 

EO,  70,  Z0  —  impressed  e.m.f.,  current  and  self -inductive  im- 
pedance respectively  of  the  primary  circuit, 

/!,  Z±  =  current  and  self -inductive  impedance  of  the  secondary 
energy  circuit, 

72,  Zx  =  current  and  self -inductive  impedance  of  the  secondary 
magnetizing  circuit, 

73  =  current  in  the  condenser  circuit,  or  tertiary  circuit, 

Zs=r3-\-  j  x&  —  total  effective  impedance  (leading)  of  the 
condenser  circuit, 

Z  =  mutual-inductive  impedance, 

ut  =  position  angle  between  the  axes  of  primary  and  tertiary 
circuit, 


STEIN  AIETZ:     ALTERNATING-CURRENT  MOTORS.  341 

a  =  speed. 

The  equations  of  the  motor  then  are: 
Primary  circuit: 

E0  =  Z0I0  +  Z  (I0  —  7X  —  73  cos  «,)_  (1) 

Secondary  energy  circuit : 

o  =  Z1I1  +  Z  (/!  — /0  +  78coBa,)  +jaZ  (72  — I88in")  (2) 
Secondary  magnetizing  circuit: 

o  =  ZlI2  +  Z  (72  — 73sin«0  +jaZ  (I,  —  70  +  73  cos  «,)  (3) 
Tertiary  or  condenser  circuit: 

o  =  Zz  Is-{-  Z  (I3  — 70  cos  w  -f-  71  cos  <w  — 12  sin  w)         (4) 

These  four  linear  equations  give  the  four  currents: 

•*OJ   *U   -*2>  -*3  • 

and  thereby  the  e.m.f  ?s.  of  rotation: 

E\  =  jaZ  (72  —  73  sin  «)  (5) 

'St=jaZ  (A— /O  +  /,CQB«)  (6) 

end  therefrom  the  torque,  power  output,  input,  etc. 
Usually  a*  is  made  60  deg.  in  this  type  of  motor. 

(4)  Polyphase  Shunt  Motor. 

Since  the  characteristics  of  the  polyphase  motor  do  not  depend 
upon  the  number  of  phases,  here,  as  in  the  preceding,  a  two-phase 
system  may  be  assumed :  that  is,  a  two-phase  stator  winding  acting 
upon  a  two-phase  rotor  winding,  that  is  a  closed  coil  rotor  wind- 
ing connected  to  the  commutator  in  the  same  manner  as  in  direct- 
current  machines,  but  with  two  sets  of  brushes  in  quadrature  posi- 
tion excited  by  a  two-phase  system  of  the  same  frequency.  Me- 
chanically the  three-phase  system  here  has  the  advantage  to  re- 
quire three  sets  of  brushes  only  instead  of  four  with  the  two-phase 
system,  but  otherwise  the  general  form  of  the  equations  and  con- 
clusions are  not  different. 

Let  E0  and  /  E0  =  e.m.f's.  impressed  upon  the  stator,  Et  and 
;  E!—  e.m.f  Js.  impressed  upon  the  rotor,  to0  =  phase  angle  between 
e.m.f.  EQ  and  E^  and  ">!=  position  angle  between  the  stator  and 
rotor  circuits.  The  e.m.f's.  E0  and  ;  E0  produce  the  same  rotating 
m.m.f.  as  two  e.m.f's.  of  equal  intensity,  but  displaced  in  phase 
and  in  position  by  angle  o>0  from  E0  and  /  E0,  and  instead  of  con- 
sidering a  displacement  of  phase  <»0  and  a  displacement  of  position 
«>i  between  stator  and  rotor  circuits,  we  can,  therefore,  assume 
zero-phase  displacement  and  displacement  in  position  by  angle 
<"<>  -f  wi  =  ">.  Phase  displacement  between  stator  and  rotor 
e.m.f  s.  is,  therefore,  equivalent  to  a  shift  of  brushes. 


8TEINMETZ:     ALTERNATING-CURRENT  MOTORS. 


Without  losing  in  generality  of  the  problem,  we  can,  therefore, 
assume  the  stator  e.m.f's.  in  phase  with  the  rotor  e.m.fs.,  and  the 
polyphase  shunt  motor  can  thus  be  represented  diagrammatically 
by  Fig.  7. 

Let,  in  the  polyphase  shunt  motor,  shown  two-phase  in  diagram 
Fig.  7: 

EQ  and  jE0,  I0  and  ;70,  Z0=  impressed  e.m.f  s.,  currents  and 
self-inductive  impedance  respectively  of  the  stator  circuits, 


Jit 


FIG.  7.  —  POLYPHASE  SHUNT  MOTOR. 

cE0  and  jcE0,  1^  and  ;71?  Z^=  impressed  e.m.f's.,  currents  and 
self-inductive  impedance  resp.  of  the  rotor  circuits,  reduced  to  the 
stator  circuits  by  the  ratio  of  effective  turns  c, 

Z  =  mutual-inductive  impedance, 

a  =  speed,  hence  :    s  =  1  —  a  =  slip, 

w=  position  angle  between  stator  and  rotor  circuits,  or  "  brush 
angle." 

It  is  then: 
Stator: 

E0=  Z0  70+  Z  (70—  7t  cos  a,  +  /7±  sin  «,) 
Rotor  : 

cEf=ZJi+Z    (/!—/„   COB«—  jig  sin  »)+jaZ 
70  sin  «>  —  ;70  cos  ^) 
Substituting  : 


(l) 


ff  =  cos 
d  =  cos 


it  ifl- 

ff6r 

and: 


a>  -fjF  sin  <o  \ 
w  —  j  sin  at  j 


0=  Z.J.+  Z  (/,-  * 
=^7,+  *^  (7, 


-  a 


it-  j    7.) 


.  . 
'  / 

(4) 

(5) 


STEIN METZ:     ALTERNATING-CURRENT  MOTORS.  343 

Herefrom  follows: 

r  ™  (*+*G)Z+Zl  ,-* 

0 


for:  c  =  of  this  gives: 

/o  — 


sZZ0+ZZi+ZoZi 

*z 


0  sZZo+ZZv+ZoZ, 
that  is,  the  polyphase  induction  motor  equations  of  page  83  et  seq., 

ff  =  cos  at  +  j  sin  at  =  1  2^  representing  the  displacement  of  posi- 
tion between  stator  and  rotor  currents. 

This  shows  the  polyphase  induction  motor  as  a  special  case  of 
the  polyphase  shunt  motor,  f  or :  c  =  o. 
The  e.m.f ?s.  of  rotation  are : 

hence: 


The  power  output  of  the  motor  is: 


[*ZZo+ZZi+ZoZi]2/ 
which,  suppressing  terms  of  secondary  order,  gives: 

p      «002  z?  j^i  +i-(x0  sin  at — r0cos  w))+c(rl  cos  at-\-Xi  sin  «*— cr0)} 


for:  c  =  o,  this  gives: 
p 

the  same  value  as  for  the  polyphase  induction  motor. 
The  power  output  becomes  zero:  P  —  o,  for  the  slip: 

TI  cos  to  -f  a?!  sin  at — cr0 

*o= — c  — : — -. s x  (10) 

TI  +c(a?0  sin  ce» — r0  cos  at) 

This  slip  *0  =o,  or  the  motor  output  becomes  zero  at  synchronism, 
if: 

r±  cos  «  +  as,   sin  o»  —  cr0  =  o 

hence : 


344  STEIN METZ:     ALTERNATING-CURRENT  MOTORS. 

or,  substituting : 

— L  =  tan  «! ,  (12) 

r.  x       '        • 


where  ^   is  the  phase  angle  of  the  rotor  impedance,  it  is: 


—  COS  (at  —  a;)  (13) 

r 


or: 


cos  («!—«;)  =  -     c.  (14) 

That  is: 

At  given  brush  angle  w,  a  value  of  secondary  impressed  e.m.f  j 
cE0,  exists,  which  makes  the  motor  tend  to  synchronize  at  no  load, 
and: 

At  given  rotor  impressed  e.m.f.;  cEQ,  a  brush  angle  w  exists, 
which  makes  the  motor  synchronize  at  no  load. 

Since  r0  is  usually  very  much  smaller  than  z»  if  c  is  not  very 
large,  it  is: 

COS    (a  —  ta)=0t 

hence  : 

«>=W0—ai  (15) 

That  is,  if  the  brush  angle  <»   is  complimentary  to  the  phase 

angle  of  the  self  -inductive  rotor  impedance    a^  the  motor  tends 

toward  approximate  synchronism  at  no  load. 
The  rotor  current: 


'0sZZ0+ZZi+Z0Zi 

becomes  zero,  if: 


or,  since  Z0  is  small  compared  with  Z,  approximately: 
c=  —  ff  8=  —  s  (cos  <w  +  j  sin  <*>) 

hence,  resolved: 
c  =  —  s  cos  of 
o  =  s  sin  o» 

hence  : 


That  is,  the  rotor  current  can  become  zero  only  if  the  brushes  are 
set  in  line  with  the  stator  circuit  or  without  shift,  and  in  this  case 
the  rotor  current,  and  therewith  the  output  of  the  motor,  becomes 
zero  at  the  slip  s  =  —  c. 


STEIN  METZ:     ALTERNATING-CURRENT  MOTORS.  345 

Hence  such  a  motor  gives  a  characteristic  curve  very  similar  to 
that  of  the  polyphase  induction  motor,  except  that  the  stator  tends 
not  toward  synchronism  but  toward  a  definite  speed  equal  to 
(1  +  c)  times  synchronism. 

The  speed  of  such  a  polyphase  motor  with  commutator  can, 
therefore,  be  varied  from  synchronism  by  the  insertion  of  an  e.m.f  . 
in  the  rotor  circuit,  and  the  percentage  of  variation  is  the  same 
as  the  ratio  of  the  impressed  motor  e.m.f.  to  the  impressed  stator 
e.m.f.  A  rotor  e.m.f.  in  opposition  to  the  stator  e.m.f.  reduces, 
in  phase  with  the  stator  e.m.f.  increases  the  free  running  speed 
of  the  motor.  In  the  former  case  the  rotor  impressed  e.m.f.  'is 
in  opposition  to  the  rotor  current,  that  is  the  rotor  returns  power 
into  the  system  in  the  proportion  in  which  the  speed  is  reduced, 
and  the  speed  variation,  therefore,  occurs  without  loss  of  efficiency, 
and  is  similar  in  its  character  to  the  speed  control  of  a  direct-cur- 
rent shunt  motor  by  varying  the  ratio  between  the  e.m.f.  im- 
pressed upon  the  armature  and  that  impressed  upon  the  field. 

Substituting  in  the  equations: 


it  is: 


r  —  IT*  iZ  ~\~  Zi  /i  o\ 

^ 


fl  = 


i—. 

~l*ZZo+ZZi+ZoZilp 

These  equations  are  very  similar  to  the  polyphase  induction  motor 
equations. 

The  stator  current: 


can  be  resolved  into  a  component: 


ri  __    jjr  _  s  Z  ~r  Zi  _  /oi\ 

^ 


which  does  not  contain  c,  and  is  the  same  value  as  the  primary  cur- 
rent of  the  polyphase  induction  motor,  and  a  component: 


(22) 


340  STEINMETZ:     ALTERNATING-CURRENT  MOTORS. 

Resolving  /o11,  it  assumes  the  form: 

/j*fcsJ(>44i^/£t;) 

=  c^Ai  cos  u>-\-  Az  sin  at)  —  j  (At  sin  at  —  A2  cos  o>)  i 

Hence,  by  choosing: 

AI  cos  01  +  42  sin  <i>  =  o 
or: 

tan*——  41  (23) 

^2 

it  is: 


Hence  this  component  can,  by  choosing  <w,  be  made  wattless, 
and  by  choosing  c,  any  desired  positive  or  negative,  that  is  lagging 
or  leading  value,  can  be  given  to  it.  The  wattless  lagging  com- 
ponent of  70  can,  therefore,  be  compensated  by  a  leading  value  of 
70U,  that  is  unity  power  factor  produced,  or  overcompensated,  that 
is  the  main  current  made  leading. 

If: 


i]  (25) 

gives  unity  power  factor,  higher  values  of  c  give  leading,  lower 
lagging  current,  and  by  varying  c,  a  phase  characteristic  of  the 
polyphase  shunt  motor  can  be  produced,  closely  resembling  the 
V-shaped  phase  characteristic  of  the  synchronous  motor  produced 
by  varying  its  field  excitation. 

Such  phase  characteristics  of  polyphase  shunt  motors  have 
been  observed. 

In  the  exact  predetermination  of  the  characteristics  of  such  a 
motor,  the  effect  of  the  short-circuit  current  under  the  brushes  has 
to  be  taken  into  consideration,  however.  When  a  commutator  is 
used,  by  the  passage  of  the  brushes  from  segment  to  segment  coils 
are  short-circuited.  Therefore,  in  addition  to  the  circuits  con- 
sidered above,  a  closed  circuit  on  the  rotor  has  to  be  introduced  in 
the  equations  for  every  set  of  brushes.  Eeduced  to  the  stator 
circuit  by  the  ratio  of  turns,  the  self-inductive  impedance  of  the 
short-circuit  under  the  brushes  is  very  high,  the  current,  therefore, 
small,  but  still  sufficient  to  noticeably  affect  the  motor  character- 
istics, at  least  at  certain  speeds.  Since,  however,  this  phenomenon 


STEINMETZ:     ALTERNATING-CURRENT  MOTORS. 


347 


will  be  considered  in  the  chapters  on  the  single-phase  series  and 
repulsion  motors,  it  may  be  omitted  here. 

(5)   Polyphase  Series  Motor. 

If  in  a  polyphase  commutator  motor  the  rotor  circuits 
are  connected  in  series  to  the  stator  circuits,  entirely  differ- 
ent characteristics  result,  and  the  motor  no  more  tends  to 
synchronise,  as  the  induction  motor  with  short-circuited  sec- 
ondary, nor  approaches  a  definite  speed  at  no  load,  as  a  shunt 
motor,  but  with  decreasing  load  the  speed  increases  indefi- 
nitely. In  short,  the  motor  has  similar  characteristics  as  the 
direct-current  series  motor.  In  this  case,  as  in  the  following  in- 
vestigations of  single-phase  alternating-current  motors,  we  may 


FIG.  8. —  POLYPHASE  SEMES  MOTOB. 

assume  the  stator  reduced  to  the  rotor  by  the  ratio  of  effective 
turns. 

Let  then,  in  the  motor  shown  diagrammatically  in  Fig.  8 : 

E0  and  jE0, 10  and  j!Q)  ZQ  =  impressed  e.m.f  s.,  currents  and  self- 
inductive  impedance  of  stator  circuits,  assumed  as  two-phase,  and 
reduced  to  the  rotor  circuits  by  the  ratio  of  effective  turns,  c, 

EI  and  jEly  1^  and  jll9  Zx  =  impressed  e.m.fs.  currents  and 
self -inductive  impedance  of  rotor  circuits, 

Z  —  mutual-inductance  impedance, 

a  =  speed  and :  s  —  1  —  a  =  slip, 

at  =  brush  angle, 

c  =  ratio  of  effective  stator  turns  to  rotor  tarns. 
If  then : 
E  and  jE  =  impressed  e.m.f 's.,  I  and  //  =  currents  of  motor,  it  is : 

7,  =  7  (1) 

70  =  c7  (2) 


348  8TEINHETZ:    ALTERNATING-CURRENT  MOTORS. 

cE0  +  E1  =  E  (3) 
and,  stator: 

E0  =  Z,  /„  +  Z  (I,  -  1,  cos  «+  fll  sin  .)'  (4) 

rotor  : 

E,  =  Z1Il  +  Z  (I,  —  IQ  cos  «  —  ;J0  sin  »)  +  /«  Z  (/It  + 

70sin  w  —  ;70  cos  a».)  (5) 
and,  e.m.f  .  of  rotation  : 

^  —  jaZ  (//!  +  70  sin  at  —  jlt  cos  «)  (6) 
Substituting  (1),  (2)  in  (4),  (5),  (6),  and  (4),  (5)  in  (3),  gives: 

/==  (c'Zo  +  ZO  +  ZU  +  c8—  2c  oosa.)  +  aZ  (o*—  1)  (7) 

where  : 

<r  =cos  w  +J  sin  at  (8) 

and: 


.  . 
V  j 


and  the  power  output: 
f—/Mf.tJ* 

a  &  \c  (r  cos  to  -\-  x  sin  w)  —  r  ( 


<*>*<*>)  +  aZ  (*  — 
a  ia  (r  c°s  w  +  a?  sin  «>  —  r) 


For  :  c  =  1,  or  equal  number  of  effective  turns  in  stator  and  rotor, 
it  is: 

TJ1 

.     . 

~[Zo  +  Zi  +  *Z  (l—  cos  w)  +  oZ^  —  i)]1 
The  characteristics  of  this  motor  entirely  vary  with  a  change  of 

ae2r  (c  —  1)   . 
the  brush  angle  «*.    It  is,  for  :  <*>  —  <r  :  P==  -  fjjvi  —  >  hence  very 

considerable. 


email,  while  for  *»  =90°:  P=—    r2  —  ,  hence 


Some  brush  angles  give  positive  P:  motor,  others  negative  P; 
generator. 

Substituting  in  (7)  for  Z,  etc.,  it  is  : 

j-'—L.  _  %  _ 

jc2  r0  +  TI  +  r  (1  -f  c2  —  2  c  cos  w)  +  a  (c(r  cos  w  +  a;  sin  o») 


_r)  J—  J|  c2  x0  +Xi  +  a;  (1  -»-  c2  —  2  c  cos  a>)  +  a  (c(»  cos  « 


—  r  sin  a>)  —  a)  ^ 


STEIN METZ:     ALTERNATING-CURRENT  MOTORS. 


349 


hence  the  angle  of  lag  of  the  current  input  behind  the  impressed 
e.m.f.  is  given  by: 

_c2  x0  +  xl  -f  x  (1  -f-c2  —  2c  cos   o>)  -f  a  (c  a;  cos  a*  —  r 

~ '  <?  r0    +r1-fr(l-|-c2~2c  cos  o>)  -f  a  (c(r  cos  w  +  x 

sin  w)  —  aj) 


sin 


—  r) 


(14) 


In  such  a  motor,  by  choosing  o»  and  c,  appropriately  unity  power 
factor  or  leading  current  as  well  as  lagging  current  can  be  pro- 
duced. The  limits  of  this  paper,  however,  do  not  permit  a  further 
discussion  of  the  very  interesting  characteristics  derived  by  choosing 
different  values  of  c  and  «>  in  polyphase  as  well  as  single-phase  shunt 
and  series  motors,  and  an  investigation  of  the  effect  of  the  short- 
circuit  current  under  the  commutator  brushes. 


I: 


POLYPHASE  SERIES  MOTOR 
40  VOLTS 


30 
40  20 
20  10 


As  instance  as  shown  in  Fig.  9,  with  the  speed  as  abscissae,  and 
values  from  standstill  to  over  double  synchronous  speed,  the  char- 
acteristic curves  of  a  polyphase  series  motor  of  the  constants: 

e  =  640  volts 

Z  —  1  —  10  j  ohms 

Z0  =  Z1  =  .I  —  .3;  ohms 


01=  37°  (sin  to  =  .6  ;  cos  w  =  .8) 


350  STEIN METZ:     ALTERNATING-CURRENT  MOTORS. 

hence: 

640 

— n-^r  *mP** 


5.8a) 

4673a 


kw. 


(.6  +  5.8a,2  +  (4.6—  2.6a)2 

As  seen,  the  motor  characteristics  are  similar  to  those  of  the 
direct-current  series  motor :  very  high  torque  in  starting  and  at  low 
speed,  and  a  speed,  which  increases  indefinitely  with  the  decrease 
of  load.  That  is  the  curves  are  entirely  different  from  those  of 
the  induction  motors  shown  in  the  preceding.  The  power  factor 
is  very  high,  much  higher  than  in  induction  motors,  and  becomes 
unity  at  the  speed:  a  =  1.7 7,  or  about  one  three-quarter  syn- 
chronous speed. 

IV. 

SINGLE-PHASE  COMMUTATOR  MOTORS. 

In  polyphase  motors  and  motors  of  similar  type  a  distributed 
rotor  and  stator  winding  is  used,  that  is  a  structure  having  uniform 
magnetic  reluctance  and  thus  exciting  impedance  in  all  directions, 
and  a  polar  construction  of  the  stator  winding  results  in  lower 
power  factor,  and  thus  is  permissible  only  in  very  small  motors 
—  as  fan  motors,  etc.  In  direct-current  motors  a  polar  construc- 
tion of  the  stator  is  almost  exclusively  used,  that  is  a  construction 
in  which  the  reluctance  in  the  direction  of  the  magnetic  field,  which 
produces  the  e.m.f.  of  rotation,  is  very  much  smaller  than  in  the 
direction  at  right  angles  thereto.  In  single-phase  alternating  com- 
mutator motors  (as  series  motors,  repulsion  motors,  etc.)  both 
stator  constructions  may  be  used,  and  in  the  most  general  case 
we  must,  therefore,  assume  the  magnetic  reluctance  and  so  the 
exciting  impedance  in  the  direction  of  the  axis  of  the  rotor  cir- 
cuits Z'  as  different  from  the  exciting  impedance  Z  at  right  angles 
to  this  axis.  When  different,  the  latter  Z  is  usually  far  larger  than 
the  former  Z' ',  since  Z  is  in  the  direction  of  the  magnetic  flux  which 
produces  the  e.m.f.  of  rotation,  that  is  corresponds  to  the  field 
excitation,  while  in  the  direction  of  Z'  energy  transfer  between 
stator  and  rotor,  or  compensation  of  rotor  reaction  takes  place, 
but  magnetic  flux  in  the  direction  Z'  does  not  produce  e.m.f.  and 
thereby  power  by  the  rotation  of  the  motor. 

The  stator  winding  can,  therefore,  be  considered  as  consisting 


8TEINMETZ:     ALTERNATING-CURRENT  MOTORS. 


of  two  components,  or  may  be  constructed  of  two  separate  circuits, 
in  the  directions  in  line  and  at  right  angles  to  the  rotor  winding, 
which  circuits  may  be  connected  in  series  or  energized  in  any 
other  manner,  as,  for  instance,  by  exciting  one  by  the  impressed 
e.m.f.,  short-circuiting  the  other  upon  itself,  etc.  With  a  com- 
pletely distributed  winding  and  an  angle  ">  between  the  axes  of  the 
stator  and  the  rotor  circuits  (the  angle  of  brush  position),  the 
exciting  or  magnetizing  component  of  the  stator  winding  is  70 
sin  at ,  the  compensating  or  power  transferring  component  70  cos  «> 
if  70=  stator  current,  as  shown  in  diagram  Fig.  10.  When  using 
separate  circuits  for  the  two  stator  components,  they  can  even 
magnetically  be  arranged  differently,  as,  for  instance,  a  unitooth 
or  polar  arrangement  chosen  for  the  field  exciting  circuit,  a  dis- 


'o<  *       ,0 


FIG.  10. 


FIG.  11. —  SINGLE-PHASE 

SERIES   MOTOB. 


tributed  winding  for  the  compensating  circuit.  In  this  case  ob- 
viously, when  reducing  all  circuits  to  each  other  by  the  ratio  of 
effective  turns,  the  resultant  vector  of  the  distributed  winding  has 
to  be  used. 

As  limit  case,  with  zero  compensating  winding,  appears  the 
plain  uncompensated  series  motor,  consisting  of  a  polar  field  ex- 
citing circuit  and  an  armature  with  brushes  at  the  neutral  or  at 
right  angles  to  the  field,  as  shown  in  Fig.  11;  as  a  further  limit 
case,  a  motor  with  zero  field  exciting  winding  on  the  stator  and 
excitation  of  the  rotor  by  a  second  system  of  brushes  at  right 
angles  to  the  main  or  power  brushes,  as  shown  diagrammatically 
in  Fig.  12. 

In  alternating-current  commutator  motors,  especially  of  the 
single-phase  type,  the  short-circuit  current  in  the  coils  under  the 
brushes  during  commutation  has  to  be  taken  into  consideration. 
While  with  numerous  commutator  segments,  carbon  brushes  and 
possibly  an  additional  resistance  in  the  commutator  leads,  as 


352 


STEIN METZ:     ALTERNATING-CURRENT  MOTORS. 


occasionally  used  in  such  motors,  these  short-circuit  currents  may 
be  moderate,  they  still  are  sufficient  to  noticeably  affect  the  con- 
stants of  the  motor,  especially  at  high  speeds,  where  the  mail] 
current  is  small,  and  at  standstill,  where  the  main  magnetic  flux 
is  very  large.  Furthermore,  the  character  of  the  commutation  of 


J^    12. WlNTER-ElCHBERG-LATOUB    MOTOR. 

the  motor,  and,  therefore,  its  operativeness,  depends  upon  these 
currents.  An  excessive  short-circuit  current  gives  destructive  spark- 
ing, while  zero  short-circuit  current  would  be  conducive  to  perfect 
commutation.  In  comparing  different  types  of  such  motors,  the 
investigation  of  the  short-circuit  current  under  the  brushes  is, 
therefore,  of  fundamental  practical  importance. 

In  its  most  general  form,  the  single-phase  commutator  motor 
can  thus  be  represented  diagrammatically  by  Fig.  13. 


FIG.  13. 

Let:  E0f  I0,  Z0=  impressed  e.m.f.  current  and  self-inductive 
impedance  of  magnetizing  or  exciter  circuit  of  stator  (field  coils), 
reduced  to  the  rotor  energy  circuit  by  the  ratio  of  effective  turns  c, 

EI,  /!,  Zi  =  impressed  e.m.f.,  current  and  self-inductive  imped- 
ance of  rotor  energy  circuit  (or  circuit  at  right  angles  to  70), 

772,  72,  Zz=  impressed  e.m.f.,  current  and  self-inductive  imped- 


STEIN  METZ:     ALTERNATING-CURRENT  MOTORS.  353 

ance  of  stator  compensating  circuit  (or  circuit  parallel  to  Jt;  the 
•'  cross-coil"  of  the  Eickemeyer  motor),  reduced  to  the  rotor  cir- 
cuit by  the  ratio  of  effective  turns  6, 

®v  I&>  Z±—  impressed   e.m.f.,  current  and  self  -inductive  im- 
pedance of  the  exciting  circuit  of  the  rotor,  or  circuit  parallel  to  70, 
A>  <Z*=  current  and  self  -inductive  impedance  of  the  short-circuit 
under  the  brushes  Ilf  reduced  to  the  rotor  circuit, 

75,   Z5=  current   and   self  -inductive   impedance  of   the   short- 
circuit  under  the  brushes  7W  reduced  to  the  rotor  circuit, 

Z  =  mutual  impedance  of  field  excitation,  that  is  in  the  direction 
of  70,  73,  74, 

Z1  =  mutual  impedance  of  armature  reaction,  that  is;  in  the 
direction  of  7W  72,  76. 

Z1  usually  either  equals  Z,  or  is  much  smaller  thanZ, 
74  and  76  are  very  small,  Z4  and  Z5  very  large  quantities. 
Let:     a  =  speed,  as  fraction  of  synchronism. 
The  equations  of  the  six  circuits  now  are  : 

(It+If-It).  (1) 

+  If-  h)+)aZ  (/.+  /,—  74)       (2) 
lf-lf-It).  (3) 

Bf=ZJt+Z  (Il+It—It)  +  jaZ*(If-If-It).      (4) 
o  =  Ztlt+  Z  (If-  If-  1.)  +  j  a  Z*  (I,+  If-  7.)  .      (5) 
o  =  ZJ>+  Z1  (/.+  If-  I,)  +  jaZ  (/.+  If-It).      (6) 
Substituting  : 

Z*/Z  =  At  where  4  =  1  with  a  motor  of  uniform  reluct- 
ance, (7) 


Z/Z6=ls 

where    >*4  and   ;8  are  small  quantities,  and  suppressing  terms  of 
secondary  order,  equations  (5)  and  (6)  give: 

/4  =  W  (/o  +  IB)  +Ja,A  (!B  -  Ii)  \  (») 


J8)  f  (10) 

Substituting  (9)  and  (10)  into  (1),  (2),  (3),  (4),  gives  four 
equations  containing  the  eight  quantities:  E09  Elt  E2,  ES)  70,  Iv 
72.  78,  requiring  four  further  conditions  to  be  given,  which  are  the 
conditions  of  operation  of  the  four  circuits,  and  distinguish  the 
different  types  or  modifications  of  such  single-phase  alternating- 
current  motors. 

Some  of  the  types  under  practical  considerations  at  present  are  : 
(1.)   Series  Motor: 

E  =  cEQ+  EI;  I0=  c7t;  72=  o;  78=  o. 

ELEC.  RYS.  —  23. 


354  STEINMETZ:     ALTERNATING-CURRENT  MOTORS. 

(2.)  Compensated  Series  Motor  (Eickemeyer  Motor), 
(a.)   direct  compensation: 

E  =  cE0+  EI+  bE2;  I0=  cli;  I2=  6Ji;  7,=ro. 
(b.)   inductive  compensation: 

E  =  cE0+  EI;  E2=  o;  I0=  c/1 ;  I&=  o. 
(3.)   Eepulsion  Motor  (Thomson  Motor)  : 

E  =  cE0+  bE2;  tf  t  =  o ;  cI0=  bI2 ;  Is=  o. 
(4.)   Compensated    Repulsion    Motor    (Winter-Eichberg-Latour 
Motor) : 

E=bE2+  fE3;  E,=  o;  I0=  o;  bI2=  fI3. 
(5.)   Inverted  Series  Motor: 

E  =  E,+  bE2+  fEs;  7e=  o;  1^=11,;  If=flv 
(6.)  Inverted  Repulsion  Motor: 

E  =  EI;  cE0+  bE2=  o;  cI0=  II2;  I&=o. 
(7.)   Induced  Series  Motor: 

E  =  E2;  EI+  cE0=o;  cI0=l^  Is=o. 
Types  (4.)  and  (5.)  have  two  sets  of  brushes  on  the  rotor. 
In  types  (3.)  and  (7.),  the  rotor  is  not  connected  to  the  external 
or  supply  circuit,  and  its  voltage  can,  therefore,  be  chosen  inde- 
pendent of  the  supply  voltage;  in  type  (4.),  by  feeding  circuit  E3 
through  transformer,  the  same  may  be  secured. 

Frequently  in  motors  of  uniform  reluctance :  Z*=  Z,  as  the  two 
stator  circuits  /0  and  I2  the  two  parts  of  the  same  uniformly  dis- 
tributed circuit  are  used,  and  then  c/&=tan  «,,  where  a>=  angle 
of  brush  shift. 

Only  a  few  of  the  more  important  types  can  be  discussed  in  the 
following : 

(1.)   Single-phase  Series  Motor. 

The  plain  or  uncompensated  single-phase  series  motor  is  usually 
designed  with  definite  field  poles,  similar  to  the  direct-current 
series  motor  (only  that  the  field  is  laminated  also).  The  object 
of  the  polar  construction  is  to  secure  as  low  a  value  of  Z1  and  as 
high  a  value  of  Z  as  possible,  so  as  to  reduce  the  armature  self- 
induction  which  is  not  compensated,  and  secure  a  fair  power  factor. 

Let  then,  in  the  motor  shown  diagrammatically  in  Fig.  14 : 

E  =  impressed  e.m.f.,  1  =  current,  c  =  ratio  of  effective  field 
turns  to  effective  armature  turns ; 

E0'  IQ,  ZQ,  Z  =  impressed  e.m.f.,  current,  self-inductive  and 
mutual-inductive  impedance  of  field  circuit,  reduced  to  armature 
circuit ; 


STEIN METZ:     ALTERNATING-CURRENT  MOTORS. 


355 


^u  Ii>  %\>  %*=  impressed  e.m.f.,  current,  self-inductive  and 
mutual-inductive  impedance  of  armature  circuit; 

74,  Z±=  current  and  self-inductive  impedance  of  the  short-cir- 
cuit under  the  brush,  reduced  to  the  armature  circuit. 


FIG.  14.  —  SINGLE-PHASE  SERIES  MOTOB. 


a  =  speed. 

Z/Zt=l  =  ^— 
It  is  then: 

E  =  c 
I0=cl 


Hence: 


And: 


^1=^1  h+Z*It+jaZ  (70-74) 
0  =  Z.  74+  Z  (74—  70) 


E 


I,  =  1(1  e—ja 


(1) 

(2) 
(3) 
(4) 
(5) 
(6) 

(7) 


c2  (Z+  Z0)  +  <Z'  +  Zi)  +ja«Z—Z  (e  +ja>  (el—jai.1) 


Or,  denoting: 


Z,  +  Z'  +  Z  (o  +ja)  (c 


(9) 

(10) 


The  e.m.f.  of  rotation  of  the  main  circuit  is 


D 


(12) 


350  STEIN  METZ:     ALTERNATING-CURRENT  MOTORS. 

of  the  short-circuit  under  the  brush: 


The  power  output  of  the  motor  is  the  algebraic  sum  of  the  power 
of  the  main  rotor  circuit,  and  that  of  the  short-circuit  under  the 
brush,  hence  is: 


.1,'--.^1/1    ( 


and  since: 

. 

/JZI,  l/*= 


it  is: 
_ 


and  the  torque  : 


)( 


(15) 

In  the  equation  of  the  current  (8), 
c-  (Z0+  Z)  is  the  total  impedance  of  the  field, 
Zt+  Z1  is  the  total  impedance  of  the  armature,  hence  : 
c2  (#0+  ^)  +  (^i+  ^)  is  the  t°tal  impedance  of  the  motor,  cor- 
responding to  the  e.m.f.  consumed  by  the  effective  resistance  and 
the  self-induction  of  field  and  armature, 

jacZ  corresponds  to  the  e.m.f.  of  rotation,  or  the  mechanical  work 
done  by  the  motor,  and 

Z  (c  +  ja)    (d  —  jaP)  is  the  effect  of   the  short-circuit  current 
under  the  commutator  brush. 


STEIN  METZ:     ALTERNATING-CURRENT  MOTORS.  357 

Neglecting   the    short-circuit   current   of   commutation,   as    of 
secondary  order,  it  is  : 

/= 

1 


-ocr 
(16) 

hence,  the  angle  of  lag  of  the  current  I  behind  the  impressed  e.m.f. 
E  is  given  by: 


With  increasing  speed  a,  the  numerator  decreases,  the  denomina- 
tor increases,  hence  the  angle  of  lag  <f>  decreases  and  the  power 
factor  cos  <f>  increases. 

The  power  factor  of  the  motor  becomes  unity,  or  <£  =  0,  at  the 
speed: 

__*(*+*.  )+(*•  +».) 

cr 

That  is  at  some  very  high  speed  the  power  factor  of  the  single- 
phase  alternating-current  series  motor,  even  if  not  compensated, 
would  become  unity,  if  there  were  no  commutation  losses. 

On  first  sight  this  is  unexpected,  since  even  assuming  the  arma- 
ture as  entirely  non-inductive,  in  addition  to  the  e.m.f.  induced 
in  the  armature  by  the  rotation  through  the  alternating  magnetic 
field,  and  in  phase  thereto,  in  the  field  coils  a  quadrature  e.m.f. 
must  be  induced  by  the  same  magnetic  flux,  and  while  the  former 
increases  relatively  to  the  latter  with  the  speed,  the  quadrature 
e.m.f.  obviously  never  can  become  zero. 

The  explanation  is  found  in  the  following:  In  equation  (17) 
the  denominator  contains  the  effective  exciting  resistances  r  as 
factor,  which  represents  the  hysteretic  loss  in  the  motor,  and  if 
r  =  o,  or  no  hysteresis  loss,  unity  power  factor  would  be  reached 
only  at  infinite  speed.  Due  to  the  hysteresis  loss  in  the  alternat- 
ing magnetic  field,  when  considering  equivalent  sine  waves,  the 
magnetic  flux  lags  behind  the  magnetizing  current  by  the  angle  of 
hysteretic  lag  «,  and  the  e.m.f.  of  rotation,  which  is  in  phase  with 
the  magnetic  flux,  therefore,  lags  behind  the  current,  that  is  the 
current  leads  the  e.m.f.  of  rotation,  and  so  at  a  certain  definite 
speed  compensation  for  the  lag  due  to  the  e.m.f.  of  self-induction 
in  the  motor  takes  place  by  the  lead  of  the  e.m.f.  of  rotation  ahead 
of  the  magnetizing  current,  which  in  this  case  is  the  main  current 


358  STEIN  METZ:     ALTERNATING-CURRENT  MOTORS. 

of  the  motor.  This  feature  is  found  in  nearly  all  types  of  single- 
phase  commutator  motors,  that  is  at  a  certain  high  speed,  when 
neglecting  commutation  losses,  the  current  is  in  phase  with  the 
impressed  e.m.f.  (and  at  still  higher  speed  leading),  and  when 
considering  equivalent  sine  waves  the  power  factor  is  unity.  Con- 
sidering the  actual  wave  shape,  however,  there  remains  a  wattless 
component  which  represents  the  wave-shape  distortion  caused  by 
the  hysteretic  cycle  of  the  magnetic  field.  It  also  follows  that  in 
all  such  single-phase  commutator  motors  a  certain  wave-shape  dis- 
tortion must  take  place,  since  the  e.m.f.  of  rotation  is  of  the  same 
wave  shape  as  the  magnetic  field  flux,  but  the  magnetic  field  flux 
and  the  current  differ  in  wave  shape  by  the  wave-shape  distortion 
represented  in  the  hysteretic  cycle  of  the  magnetic  structure. 

At  given  speed  a,  the  power  factor  is  a  maximum  for  that  value 
of  c,  where: 


substituting    (17),  and  suppressing  quantities  of  higher  order, 
this  gives: 

rx1+xrl     .     /  yxl  -\-  rrl 


l     .     /  yxl 


or  approximately,  for  higher  speeds  a  : 


(20) 


Since  Z*<Z,  condition  of  good  power  factor  of  an  uncompen- 
sated  single-phase  series  motor  is:  c<l,  that  is,  low  field  excita- 
tion and  high  armature  reaction.  Let,  for  instance,  Z  =  1  —  10;', 
Z*=.2-5 —  2.5;,  it  is:  o*=.5,  or  the  number  of  effective  arma- 
ture turns  equals  twice  the  number  of  effective  field  turns. 

As  an  instance  are  shown,  in  Fig.  15,  with  the  speed  a  as  ab- 
scissae, and  for  values  up  to  above  double  synchronism,  the  char- 
acteristic curves  of  a  single-phase  series  motor  of  the  constants: 

e  =  800  volts. 

Z  =  l  —  10;  ohms 

Zl=.25  —  2.5;  ohms 

Zf=  .1  —  .3;  ohms 

Z0=  A  —  1.2;  ohms 

Z4=  30  —  30;  ohms,  hence :  A  =  .18  —  .15;;  A'=.045  —.038; 


STEIN METZ:     ALTERNATING-CURRENT  MOTORS. 


339 


800 


(1.03  -f  4.27fl  -f-  .35a*  )  —  j  (5.19  --  98a  —  .49a3  ) 
640a  (4.23  -f  . 


hence: 


_  _ 

~~  (1.03  +  4.27a  -f  .35a2  )2  -f-  (5.  1  9  —  .9  Ja  —  .49a2  )2 
As  seen,  at  very  high  speeds,  power  factor  p  and  efficiency  y  reach 
very  good  values. 

The  curves  are  similar  to  those  of  the  direct-current  series  motor, 
except  that  with  increasing  speed,  current,  torque  and  power  fall 


SINGLE  PHASE 

SERIES  MOTOR 

800  VOLTS 


T:P: 

I:*: 
230 

120 
110 
100 

90 


ro 


.4          .6          .8          1.0 


1.4        1.6        1,8        2.0 


FIG.  15. 


off  rather  slower,  that  is,  the  motor  tends  more  toward  racing  at 
light  load. 

(2)  Compensated  Series  Motor  (Eickemeyer  Motor). 

To  secure  good  power  factors  in  a  single-phase  series  motor,  u 
low  field  self-inductance,  that  is  low  number  of  field  exciting  turns, 
is  necessary,  and,  therefore,  a  high  number  of  armature  turns,  to 
get  the  required  output.  Increasing  the  ratio  of  the  armature  re- 
action to  field  excitation,  a  limit  is  reached,  where  the  increase 
of  armature  self-inductance  overbalances  the  decrease  of  field  in- 
ductance, and  the  power  factor  again  decreases.  In  the  preceding 
instance  shown  in  Fig.  15  this  limit  is  reached  at  an  armature 


300  STEINMETZ:     ALTERNATING-CURRENT  MOTORS. 

reaction  equal  to  about  twice  the  field  excitation,  and  at  this  pro- 
portion the  power  factor  is  highest,  but  still  rather  poor  at  lov/ 
and  moderate  speeds.  Better  proportions  may  possibly  be  reached 
by  different  design,  but  in  this  feature  the  limitation  of  the  plain 
series  motor  is  found :  in  the  limited  armature  reaction  permissible 
by  armature  self-induction.  By  compensating  for  the  armature  re- 
action and  so  more  or  less  completely  neutralizing  its  self-induction, 
a  higher  ratio  of  armature  reaction  to  field  excitation  and  so  better 
power  factors  may  be  secured.  The  armature  self-induction  is  com- 
pensated by  surrounding  the  armature  by  a  stationary  circuit, 
through  which  a  current  passes  in  opposite  direction  to  the  current 
in  the  armature.  This  compensating  circuit  may  either  be  energized 
by  the  main  current  in  series  to  the  armature,  or  by  a  secondary  cur- 
rent, by  closing  it  upon  itself  in  short-circuit.  The  compensated 
series  motor  then  contains  a  field  exciting  coil  in  quadrature  posi- 
tion to  the  armature  circuit  and  a  compensating  coil  in  line  with 
the  armature  circuit.  The  field  may  be  a  polar  structure  as  in  the 
Eickemeyer  motor  of  1890,  or  a  distributed  winding.  The  com- 
pensating circuit  preferably  has  a  distributed  winding,  since  it 
should  neutralize  the  distributed  armature  winding.  Frequently 
in  such  motors  a  uniformly  distributed  stator  winding  is  used,  of 
which  one  section  is  used  for  field  excitation,  the  other  for  com- 
pensation, by  using  either  separate  coils,  or  the  same  coil,  tapping 
into  it  at  an  angle  &  with  the  direction  of  the  rotor  circuit. 

When  compensating  by  passing  the  main  current  through  the 
compensating  circuit  in  series  to  the  armature  circuit,  by  choosing 
the*  number  of  turns  of  the  compensating  circuit,  under-compensa- 
tion,  or  overcompensation,  or  complete  compensation  can  be 
secured.  Complete  compensation  obviously  gives  the  best  power 
factor.  Some  valuable  features,  however,  are  produced  by  over- 
compensation. 

When  compensating  by  closing  the  compensating  circuit  upon 
itself,  as  secondary  short-circuit,  the  compensation  necessarily  is 
always  approximately  complete. 

(a)   Directly  Compensated  Motor. 
Let  in  the  motor  shown  diagrammatically  in  Fig.  16: 
E  =  impressed  e.m.f .,  7  =  current  of  the  motor, 
E0,  70,  Z0=  impressed  e.m.f.,  current  and  self-inductive  im- 
pedance of  field  exciting  circuit,  reduced  to  the  armature  circuit 
by  the  ratio  c  of  effective  field  turns  to  effective  armature  turns, 


STEINMETZ:     ALTERNATING-CURRENT  MOTORS.  :*<>! 

E19  /u  Z^==  impressed  e.m.f.,  current  and  self-inductive  im- 
pedance of  armature  circuit, 

E2,  72,  Z2,=  impressed  e.m.f.,  current  and  self-inductive  imped- 
ance of  (stationary)  compensating  circuit,  reduced  to  the  arma- 
ture circuit  by  the  ratio  of  effective  turns  &, 

74,  Zf=  current  and  self-inductive  impedance  of  the  short-cir- 
cuit under  the  commutator  brush,  reduced  to  the  armature  circuit, 


FlG.   16. —  ElCKEMETEB   MOTOB  DIBECT  COMPENSATION. 

Z  =  mutual-inductive  impedance,  constant  in  all  directions, 


(I) 
(2) 

(3) 
(4) 

(6) 
(6) 
(1) 

(8) 

(9) 
(10) 


a  =  speed. 
It  is  then  : 


I2=bl 
Field  circuit: 


Compensating  circuit: 
E^ZJi+ZV^- 
Armature  circuit: 


Brush  short-circuit: 

o=ZJl+Z  (/,-/„ 
Herefrom  follows: 


>el  approximately 


362  8TEINMETZ:     ALTERNATING-CURRENT  MOTORS. 

Main  current: 

•pi 

Zi  +  Vs  Zz  +  Z  (I-  b?    +  o  Z(c 


where  : 

D=\c*Z,+Z1+VZ2+Z(l-ir\+cZ(c+}a).(l-i)    (13) 

Short-circuit  current  under  brushes  : 

Ti==slE\c-ja(\-b)  \ 

IcE  /n  Kx 

=  —fi-    approx. 

c.m.f.  of  rotation  of  main  armature  circuit: 


e.m.f.  of  rotation  of  brush  short-circuit: 


Power  output: 


In  the  equation  of  the  current,  (11),  c2(ZQ+Z)  is  the  total 
impedance  of  the  field,  b2Z2  is  the  total  impedance  of  the  compen- 
sating circuit,  Z±-\-  Z  (\  —  &)2  is  the  total  impedance  of  the  arma- 
ture, the  component  Z(l  —  &)2  being  due  to  incomplete  compen- 
sation. In  the  uncompensated  motor  on  its  place  stands  Z1. 

Neglecting  the  effect  of  the  short-circuit  under  the  brush  in 
equation  (11),  and  substituting  for  Z,  etc.,  it  is: 


7= 


+  0V,  +  n  +  (  I  —  b^r  4-  acx  }>  —j^  c\x0  +  x) 


4-  b*  a^+Ki  -^  (  I  —  bfx  —  acr  }•  (20J 


STEINMETZ:     ALTERNATING-CURRENT  MOTORS.  3G3 

hence  the  angle  of  lag  of  the  motor  : 

_c^g0  +  g)  +  62^-t-a;H-(l  —  bYx—acr 
^(r0+r)+aS+ri+(l—  6)V+oc* 

<fr  =  o,  that  is,  unity  power  factor  is  reached  at  the  speed  : 

g      c»^+g)+^+a?i+(l—  b)*x 

cr  *     ' 

The  explanation  hereof  is  the  same  as  in  the  preceding  chapter. 
The  term  (1  —  6)2  Z  disappears,  that  is,  complete  compensation 
takes  place  for:    6  =  1. 
Substituting  6  =  1,  gives  : 

/_.  _  * 

—  acr 


At  given  speed  a,  the  power  factor  is  a  maximum,  that  is,  ^  a 
minimum,  for  the  value  of  cf  where  : 


this  gives  : 


cr  approximately,  for  higher  values  of  a: 


Z 

Since  the  self-inductive  impedance  Z^  is  very  small  compared 
with  the  exciting  impedance  Z,  c  is  a  small  fraction,  that  is,  the 
armature  reaction  of  the  completely  compensated  motor  can  be 
made  very  much  higher  than  the  field  excitation.  For  instance, 
let  :  Z  =  1  —  10;;  Z2  =  .13  —  Aj,  it  is  :  c  =  .2. 

The  e.m.f  .  of  rotation  of  the  short-circuited  coil  under  the  brush  : 


contains  the  factor  (1  —  6),  hence  disappears  at  complete  com- 
pensation, 6  =  1,  and  reverses  its  direction  by  overcompensation  : 
6  >  1.  Hence,  by  overcompensation  a  reverse  e.m.f.  can  be  inserted 
into  the  coil  short-circuited  under  the  brushes,  and  thereby  the 
commutation  controlled,  that  is,  sparkless  commutation  secured,  at 
Hie  expense,  however,  of  some  decrease  of  the  power  factor. 


364 


STEIN  METZ:     ALTERNATING-CURRENT  MOTORS. 


As  instance  may  be  considered  a  motor  of  the  constants: 
e  =  500  volts, 
Z  =  I  —  10;  ohms, 
Z1  =  .1  —  .3;  ohms, 
Z2  =  .13  —  Aj  ohms, 
ZQ  =  A  —  1.2;  ohms, 
£4  =  30  —  30;  ohms, 
A  =  .18  — .15; 
c=.25 


500 


(.4+  2.01a)—  j  (1.28—  .58a) 
502.5g 


hence : 
hence: 


_ 
-f  (1.28  —  .58a)2 

Since  the  curves  of  this  motor  are  almost  identical  with  those  of 
the  inductively  compensated  motor,  they  are  not  given. 

(&.)  Inductively  Compensated  Motor. 

Let,  in  the  motor  shown  diagrammatically  in  Fig.  17  the  denota- 
tions be  the  same  as  in  (a.),  the  directly  compensated  motor,  except 


FlG.    17.  —  ElCKEMEYEE   MOTOB   INDUCTIVE   COMPENSATION. 

that  now  72  is  a  separate,  secondary  current,  and  not  =  67,  and 
E2=  o.     It  is  then  : 

E  =  Ei  +  cE,  (1) 


Field  circuit: 


(3) 

(4) 


STEIN  METZ:    ALTERNATING-CURRENT  MOTORS.  365 

Armature  circuit: 


/.-/«)  (5) 

Compensating  circuit: 

o  =  ZJ2+Z  (!,  —  !,) 
Short-circuit  under  brush: 

o  =  ZJt  +  Z  (!<-!„)  +  jaZ  (/»-/,)  (7) 

From  (6)  follows: 


from  (7)  : 


hence  substituted  into  equations  (1)  to  (5) 
Main  current: 


Zi 


xwl     '  — ??— i 

/4  = -. • 


where  : 
D  =  c>Z0  +  Z,  +  ~z-  +  eZ  (c+ja)  (1-4)  (112) 

Short-circuit  current  under  commutator  brush: 


(13) 


=  — j —  approx. 
E.m.f.  of  rotation  of  main  circuit: 

EI   = ~: \**v 

E.m.f.  of  rotation  of  armature  short-circuited  coil: 


hence  very  small. 

Power  output,  suppressing  terms  of  secondary  magnitude: 


Torque  : 

ca;^2  /  r       \  /1    , 

r^iv  '""^  v 


3GG  STEIN METZ:     ALTERNATING-CURRENT  MOTORS. 

zz> 


As  seen,  these  equations  contain: 


instead  of:    b2 Zz  •+ 


(1 — bf  Z  of  the  directly  compensated  motor,  which   latter,  for 

7  7 

6  =  1,  gives  Z2.     Since  Z2  is  small  compared  with  Z,  -     .  L-  is 

almost  identical  with  Z2,  inductive  compensation  gives  almost  iden- 
tically the  same  results  as  complete  direct  compensation,  and  all 
conclusions  derived  under  (a.)  for  the  case  of  complete  compensa- 
tion: 6  =  1,  apply  to  the  case  of  inductive  compensation. 


800 
275 
250 
200 

irs 

150 
125 
100 


'IL 


u_ 


T\ 


\ 


\ 


EICKEMEYER  MOTOR 
500  VOLTS 


T< 

280 
260 
240 
220 
200 
180 
160 
140 
120 
100 


1.0 


1.6    1.8    2.0 


FIG.  18. 


As  instance  are  shown,  in  Fig.  18,  with  the  speed  a  as  abscissae, 
the  curves  of  an  inductively  compensated  motor  of  the  constants: 
e  =  500  volts, 
Z  =  1  —  10;  ohms, 
Z1  =  .l  —  .3;  ohms, 
Z2  =  .l3  —  Aj  ohms, 
Z0  =  A  —  1.2  j  ohms, 
Zs  =  30  —  30;  ohms,  hence  :  *  =  .18  —  .15; 


Hence: 
7  = 


500 


(.394-2.01a)  —  j  ^1.27  —  58,;) 


(.39+2.0  1  a)*  —  (1.27—  .58) 


STEIN METZ:     ALTERNATING-CURRENT  MOTORS.  367 

Interesting  is  the  very  high  power  factor  reached  already  at  low 
speed:  80  per  cent  below  half  synchronism.  At  speed:  a  =  2.19 
unity  power  factor  is  reached. 

The  starting  torque  is  very  large,  and  with  increase  of  speed  the . 
torque  falls  rapidly,  very  similar  as  in  a  direct-current    series 
motor. 

(3)  Repulsion  Motor  (Thomson  Motor). 

In  Prof.  E.  Thomson's  single-phase  repulsion  motor  the  stator 
is  supplied  with  the  main  current,  the  rotor  short-circuited  upon 
itself  through  the  commutator  brushes  under  an  angle  with  the 
axis  of  the  stator  circuit. 

Amongst  the  single-phase  commutator  motors  this  repulsion 
motor  takes  a  separate  and  distinctive  position  by  its  magnetic 
characteristics  and  their  effect  on  commutation,  so  that  single- 
phase  commutator  motors  may  be  divided  into  series  motors  and 
repulsion  motors.  While  both  types  of  motors  have  similar  speed 
characteristics,  the  magnetic  flux  of  the  repulsion  motor  is  an 
elliptically  rotating  flux,  while  that  of  the  series  motor  is  essentially 
an  alternating  flux.  In  the  series  motors  treated  in  the  preceding, 
the  magnetic  flux  in  the  axis  of  the  rotor  circuit  is  either  negli- 
gible, in  the  compensated  motor,  or  as  magnetic  flux  of  armature 
reaction  in  phase  with  the  main  magnetic  flux.  The  e.m.f.  in- 
duced in  the  armature  coil  short-circuited  under  the  brush,  by  its 
rotation,  is,  therefore,  either  negligible  or  in  phase  with  the  main 
flux,  while  that  induced  by  the  alternation  of  the  flux  enclosed 
by  the  short-circuited  coil  is  in  quadrature  with  the  main  flux, 
and  so  with  the  e.m.f.  of  rotation,  and  the  short-circuited  coil  is 
the  seat  of  an  active  e.m.f.  at  all  speeds.  In  the  repulsion  motor, 
the  magnetic  flux  in  the  direction  of  the  axis  of  the  armature 
circuit  is  in  quadrature  with  the  current  and  thereby  the  flux  at 
right  angles  with  the  armature  circuit,  but  the  former  is  constant, 
the  latter  varying  inversely  with  the  speed.  The  e.m.f.  induced  by 
rotation  in  the  coil  short-circuited  under  the  commutator  brush 
is  in  phase  with  the  quadrature  field  of  the  motor,  while  the  e.m.f. 
of  alternation  is  in  quadrature  with  the  main  field,  and  since  the 
two  fields  are  in  quadrature  with  each  other,  the  two  e.m.f  s.  in- 
duced in  the  short-circuited  coil  are  in  opposition  to  each  other, 
that  is  neutralize  each  other  more  or  less  completely.  At  synchron- 
ism the  two  e.m.f  s.  are  equal  and  opposite,  the  neutralization  com- 
plete and  commutation,  therefore,  theoretically  perfect. 


308 


8TEINMETZ:     ALTERNATING-CURRENT  MOTORS. 


The  repulsion  motor  can  be  constructed  with  distributed  or 
with  polar  stator  winding.  Since,  however,  compensation  takes 
place  of  the  armature  reaction  by  the  primary  current  and  the 
secondary  current  flowing  in  opposite  direction,  and  the  rotating 
!u.m.f.  of  the  motor  can  produce  a  uniformly  revolving  (circular 
or  elliptic)  magnetic  field  only  in  a  structure  of  uniform  reluctance, 
polar  winding  gives  decidedly  inferior  characteristics  and  a  dis- 
tributed stator  winding  is,  therefore,  assumed  in  the  following. 
With  polar  construction,  different  exciting  impedances  Z  and  Zl 
have  to  be  introduced  in  the  two  quadrature  directions. 


FIG.  19. —  THOMSON  MOTOR, 


Let,  in  a  repulsion  motor  : 

E0,  /0,  Z0  =  impressed  e.m.f.,  current  and  self-inductive  im- 
pedance of  primary  or  stator  circuit, 

Ilf  Z1  =  current  and  self  -inductive  impedance  of  secondary  or 
rotcr  circuit,  reduced  to  primary  by  the  ratio  of  effective  turns, 

74,  Z4  —  current  and  self  -inductive  impedance  of  short-circuit 
under  brush,  reduced  to  primary  circuit, 

Z  =  mutual-inductive  impedance, 


a  =  speed,  as  fraction  of  synchronism, 

to  =  angle  between  axis  of  primary  and  secondary  circuit,  or 
angle  of  brush  shift. 

It  is  then,  in  the  motor  shown  diagrammatically  in  Fig.  19. 
Stator: 

E0  =  ZJ0  +  Z0  (70  —  *i  cos  <*  —  74  sin  w)  (1) 

ttotor: 

o  ==  ZJ,  +  Zi  (7±  —  70  cos  ")  +  jaZ  (10  sin  «>  —  J4)     (2) 


STEIN METZ:     ALTERNATING-CURRENT  MOTORS.  ,309 

Short-circuit  under  brush  : 

o  =  ZJ4-{-Z4  (J4  —  J0  sin  <*>)-}- jaZ  (Jx  —  J0  cos  CM)  (3) 
hence : 

J4  =  A  |  TO  (sin  ut  +ja  cos  CM)  —  ja  Ji  f  (4) 

and,  substituting  (4)  in  (2)  : 

7         T  „  (cos  a-  ja  sin  CM) — a  A  (a  cos  CM  — ./sin  /M)  (5) 

*i  =  lo*  -  —„  -f  7.  a  A  Z 

substituting  (4)  and  (5)  in  (1)  : 

Z  Zo  -h  Zi  ~h  Z  »in  w  (»iu  w+«/^  cos  w)  (l  —  A)  (G) 

or,  denoting: 

•D  =  Z"0  +  Z^  -{-  Z"  sin  CM  (sin  CM  4-  /#  cos  <»)  (1  • —  ^)  (7) 
Primary  or  main  current: 

/o=        ~TJ>~~  (8) 

Secondary  current: 

/  — _  jg  \  (  cos  CM  -  ja  sin  co> — a  A  (a  cos  CM — j  sin  CM)  }  (9) 

~~D~ 

Short-circuit  current  under  brush : 
sin  CM 


E.m.f.  of  rotation  of  main  armature  circuit: 
E11  =  jaZ  (70  sin  w  —  J4) 


E.m.f.  of  rotation  of  short-circuit  under  brush: 
ES  =  jaZ  (A—  J0  cos  ») 

=  a  ^0  ]  a  ^(  1  —  A  )  sin  <o  —  j  Zi  cos  Q>  j"  1 

^  V  Cll) 

=  ^^fintt>     appro*.  j 

The  power  output  is  : 

P=/SA/1/'  +  /#4M4/i 

_  a  ^02sin  ut  i        ,  j 

~TZ)j«  —  1  /  -;  ]Zi+  Z  (  1  —  A)  j-  ,  (cos  w  7^  a  sin  w  )  —  a  A  (a  cos  w 

—Jsin  ai)  71  +  a  (1—  a2  )  sin  a>  /Z,  ^ 


(1  — 


ELEC.  RYS.  -  24. 


370  8TEINMETZ:     ALTERNATING-CURRENT  MOTORS. 


cos  «_a  (r+rt)  sin  *  —  ^  (x 


cos  w=ra  (Z  —  a2  )  sin  ca  )  —  >12  (1  —  a2)  (r  cos  &  —  a#  sin  o>)  !•   (12) 
As  seen,  in  the  repulsion  motor,  sin  «>  takes  the  place  of  c,  the 

ratio  of  field  exciting  turns  to  armature  turns,  of  the  series  motor. 

I  z  sin  at  is  the  field  exciting  or  magnetizing,  J0  cos  ^  the  compensat- 

ing circuit.  , 

At  synchronism  :  a  =  1,  it  is  : 

It  =  0, 

that  is,  at  synchronous  speed,  the  short-circuit  current  under  the 
commutator  brushes  of  the  repulsion  motor  is  zero,  and  the  com- 
mutation perfect. 
It  is  then  : 


Z    Zo  +Zi+  Zsin  w  (sin  <o+jco*  w)  (1—1) 
or  approximately,  neglecting  ZQ,  and 

0       Z  sin  «>(8in  at -\-j  cos  to) 
and,  absolute: 

*o  = 

and  the  power  factor: 

p=C08  (a-|-  o»— -90°) 

where :  tan  a  =  — 
r 

The  secondary  current  is: 
— j  8*n 


(sinw  -f  jcosw) 
or  absolute: 


^      ' 

-—  (17) 

*  8in« 

hence,  at  synchronism  the  secondary  current  equals  the  primary 
current,  and  leads  it  by  angle  at. 

The  power  is,  at  synchronism,  approximately: 

cos*  -(r  +  rOsina.  (18) 


that  is,  the  effect  of  the  short-circuit  under  the  brushes  disappeared. 

Since  the  repulsion  motor  contains  the  factor  (1  —  a2)  in  the 

short-circuit  current  under  the  brush,  I4,  which  does  not  appear 

in  the  series  motor,  within  the  range  where  this  factor  is  small, 


STEINMETZ:    ALTERNATING-CURRENT  MOTORS.  371 

that  is,  near  synchronism  and  below  synchronism,  the  short-circuit 
current  is  less,  and  the  commutation,  other  things  being  equal, 
better  in  the  repulsion  than  in  the  series  motor.  Considerably  above 
synchronism,  however,  where  [1 — &2]>1,  the  short-circuit  cur- 
rent of  the  repulsion  motor  becomes  large,  and  the  commutation 
inferior  to  that  of  the  series  motor.  Thus  the  repulsion  motor  is 
specially  suited  for  the  range  of  speed  from  standstill  up  to  some- 
what above  synchronism,  where  the  plain  series  motor  is  unsuitable 
by  its  lower  power  factor. 

Neglecting  the  effect  of  commutation,  it  is: 

I    -E°  Zo  +  Zi  +  Z  sin  at  (sin  at  -\-ja  cos  to)          (19) 
~  Z  Zi  +  Z 

j E0  (cos  at  -j-  fa  sin  ">) (20) 

ZQ-\- Z\  -\-Z  sin  a*  ^sin  at  ~K/a  °°8  w) 
or  approximately: 

jo= E» (21) 

Z0  +  Z\  +  Z  sin  at  (sin  at  -\-ja  cos  a>) 

K 

*o  +  ri  +  r  8in2w  -h  a  «  sin  a*  cos  a»)  — j  (x0  -j-  «i  +  x  sin2^  —  ra 


sin  w  cos  at)  (  22  ) 

or,  absolute: 


=  r^j/cos2  u;  +  a3  sin  2«>  =  -    -  |/i  —  (1  —  a*  )  sin2  «  (24) 


hence,  up  to  synchronism:  a<l,  the  secondary  current  is  less  than 
the  primary  current,  at  synchronism:  a  =  l,  both  currents  are 
equal  and  above  synchronism:  a  >  1,  the  secondary  current  is 
greater  than  the  primary  and  does  the  magnetizing  of  the  motor 
field. 

The  secondary  current  leads  the  primary  current  by  the  angle: 
tan  8  ==a  tan  at  (25) 

The  phase  angle  of  the  motor  is,  approximately,  and  neglecting 
the  effect  of  commutation: 

tan    =  X°  ~^~  Xl  ~^~  x  8*p2  *"  —  ar  8*n  w  cos  w 
r0  -|-  r\  -\-  r  sin2<y  -{-ax  sin  at  cos  at 

The  power  factor  is  a  maximum,  or  the  angle  of  lag  <£  a  mini- 
mum, for  the  brush  angle  w,  where  : 


372  8TEINMETZ:     ALTERNATING-CURRENT  MOTORS. 

Neglecting  secondary  quantities  this  gives: 
sin  at= — — 5 — — —  -f- 

<722 

rlr0+r1)+x(x0+xl)    , 


hence,  for:  a=l  or  synchronism,  if:  Z  =\ — 10;;  Z<f=Zf= 
.1— -.3;',  it  is: 
sin  w  =.235 

<»  =  13.6  deg. 
This  agrees  with  experimental  evidence. 


I: 

425 
400 
875 
850 
825 
800 
275 
250 
£25 
200 
175 
150 
125 
100 

T 

360 
340 
320 
300 
280 
260 
£:«, 

%    220 
100200 
90  180 
80160 
70  140 
60  120 
50100 
40    80 
30    60 
20   40 
20 

"^X.     r 

\ 

\ 

N 

A 

N\ 

THOMSON  MOTOR 
500  VOLTS 

V 

\ 

\ 

\ 

\i 

\   x 

v 

•  \ 

p/ 

\ 

X\ 

_. 



P 

/ 

2 

^-*       N 

"*• 

~^^- 

/  ^ 

$^ 

\ 

^ 

J 

j  ^-^ 

\ 

7 

z 

\ 

V. 

\ 

// 

Ny 

\ 

N 

^ 

// 

\ 

\ 

^"^•»,^ 

77 

> 

Xv 

\ 

/ 

\ 

^ 

\ 

/ 

^ 

^ 

[ 

A         A        l.O 
FIG.  20. 


1.2 


As  instance  are  given,  in  Fig.  20,  with  the  speed  a  as  abscissas, 
the  characteristic  curves  of  a  repulsion  motor  of  the  constants: 
e0  =  500  volts, 
Z  =  1  —  10;  ohms, 
ZQ  =  Z1=.l  —  .3  ohms, 
Zi=  30  —  30;  ohms,  hence  :    =.18  —  .15;, 
m  =  14  deg.,  or:  sin  &  =.25;  cos  to  =.97. 


8TE1NMETZ:     ALTERNATING-CURRENT  MOTORS.  373 

Hence  : 


„       478+13.8<z—  94.2az  —  24.  7a* 
=  (.88t+1.80a)*+(1.07-.845a)' 


As  seen,  the  torque  curve  is  extremely  steep,  that  is,  the  starting 
torque  higher  than  in  any  other  motor,  and  torque  and  power  be- 
come zero  at  a  definite  speed,  1.88  times  synchronism.  Power  fac- 
tor and  efficiency  are  extremely  high  at  low  speeds,  but  begin  to 
fall  off  beyond  synchronism,  though  this  falling  off  can  greatly  be 
reduced  by  limiting  74. 

V. 

In  the  diagrams  showing  as  instances  the  characteristic  curves 
of  different  types  of  motors  :  polyphase  and  single-phase  induction, 
polyphase  series,  single-phase  series,  compensated  series  or  Eicke- 
meyer  motor,  and  repulsion  or  Thomson  motor,  the  constants 
have,  so  far  as  possible,  been  chosen  so  as  to  represent  the  same 
motor  structure  :  that  is,  to  permit  a  direct  comparison  of  the  types, 
one  and  the  same  motor  is  assumed  as  operated  as  any  of  the  differ- 
ent types,  after  making  the  changes  in  its  electric  and  magnetic  dis- 
position necessary  for  this  purpose. 

In  comparing  the  power  factors  it  is  interesting  to  note  that  the 
maximum  power  factors  of  the  commutator  motors  are  decidedly 
higher  than  those  of  the  corresponding  induction  motors,  and 
that,  therefore,  the  same  power  factor  as  in  the  induction  motor 
can  be  secured  in  the  commutator  motor  with  a  much  larger  air 
gap  between  the  stator  and  rotor.  This  is  a  very  decided  advan- 
tage, especially  for  railway  work  where  induction  motor  air-gaps 
are  mechanically  extremely  undesirable  and  unsafe. 

In  Figs.  21  and  22  are  shown  for  comparison,  with  the  speed  as 
abscissae,  the  torque  and  power  of  all  the  different  motors.  In 
Fig.  21  all  the  torque  curves  are  reduced  to  equal  torque  at  95  per 
cent  of  synchronism.  In  Fig.  22  all  the  power  curves  to  the  same 
maximum  output.  Not  too  much  stress,  however,  must  be  laid  on 
these  comparative  curves  since  the  characteristics  of  each  motor 
may  be  varied  to  a  considerable  extent  by  the  design,  for  instance. 
a  motor  designed  for  the  highest  possible  efficiency,  or  highest 
starting  torque,  or  best  power  factor,  etc.  Some  general  conclu- 
sions, however,  can  be  drawn  from  these  curves. 


374 


STEIN METZ:     ALTERNATING-CURRENT  MOTORS. 


In  the  induction  motors  the  torque  curve  is  rising  with  the  speed, 
in  the  commutator  motors  decreasing.     The  commutator  motors, 


.4          .6          ,8          LO         1.2         1.4         1.6         1.8         2.0 


therefore,  give  maximum  torque  in  starting  and  at  low  speed.    The 
induction  motors  are  operative  efficiently  only  in  a  narrow  speed 


J         4         4         .8         1.0        1.2        1.4       Li        1-8        2.0 


10 


range  below  synchronism,  but  unstable  below  this;  that  is  the 
motor  either  slows  down  and  comes  to  rest  or  accelerates  with  in- 


8TEINMETZ:     ALTERNATING-CURRENT  MOTORS.  375 

creasing  rapidity  until  it  approaches  synchronism.  At  synchron- 
ism the  torque  and  power  of  the  induction  motor  reverse.  High 
torque  at  low  speeds  can  be  secured  only  at  a  sacrifice  of  efficiency 
by  armature  resistance. 

The  induction  motors  are,  therefore,  essentially  constant  speed 
motors. 

The  repulsion  motor  shows  the  highest  starting  torque  and  the 
most  rapid  decrease  of  torque  and  power  with  increase  of  speed 
and  reaches  zero  torque  and  power  at  a  definite  speed. 

The  single-phase  series  motor  shows  of  all  the  commutator  motors 
the  lowest  torque  in  starting,  the  highest  at  high  speed;  that  is, 
its  torque  decreases  least  with  increase  of  speed,  so  that  in  the  case 
illustrated  it  almost  approaches  a  constant  torque  motor. 

The  compensated  motor  is  intermediate  between  the  repulsion 
and  series  motor,  but  rather  nearer  to  the  former  at  low  and  to  the 
latter  at  high  speeds ;  that  is,  its  torque  is  high  in  starting  and  at 
low  speeds,  but  does  not  fall  off  as  rapidly  at  high  speeds  as  that  of 
the  repulsion  motor. 

To  conclude,  then,  the  induction  motors  are  essentially  constant- 
speed  motors.  The  repulsion  motor  is  a  low-speed  motor,  the  series 
motor  ,a  high-speed  motor,  while  the  compensated  or  Eickemeyer 
motor  is  intermediate  between  the  repulsion  and  series  motor,  ap- 
proaching the  former  at  low,  the  latter  at  high  speeds. 

CHAIRMAN  DTTNCAN:  The  next  paper  is  on  "Single-Phase  Motors/*  by 
Mr.  Max  DSri,  which  will  U  abstracted  by  Mr.  Slichter. 


SINGLE-PHASE  MOTOES. 


BY  MAX  DERL 


The  single-phase  motor  has  assumed  of  late  an  increasing  im- 
portance since  it  has  become  known  that  it  is  not  only  applicable 
to  traction,  but  possesses  a  peculiar  adaptability  thereto  on  account 
of  the  simplicity  of  the  design,  which  permits  of  the  use  of  high 
tension,  and  also  on  account  of  superior  regulating  and  speed  con- 
trol. 

It  is  obvious  that  we  refer  only  to  the  single-phase  motor  with 
commutator,  for  the  induction  motor  without  commutator  (the  so- 
called  asynchronous  single-phase  motor),  to  which  we  refer  in  this 
paper  only  for  the  purpose  of  comparison  and  criticism,  cannot  be 
seriously  considered  as  a  traction  motor.  Although  views  as  to 
commutator  machines  for  single-phase  currents  have  become  much 
clarified  of  late,  and  much  of  the  prejudicial  bias  against  them  over- 
come, yet  exact  knowledge  as  to  the  internal  phenomena  of  these 
machines,  particularly  those  of  commutation,  is  still  very  limited. 

In  this  paper  an  attempt  will  be  made  to  present  a  comprehensive 
review  of  the  essential  functions  and  relations  of  modern  single- 
phase  motors,  in  order  to  facilitate  a  comparison  of  the  working 
conditions  and  commutating  requirements  of  the  different  systems. 
The  presentation  of  some  new  points  of  view  may  assist  the  under- 
standing, and  the  many-sided  and  practical  value  of  single-phase 
motors  can  be  demonstrated  still  better  by  citing  several  hitherto 
unknown  methods  of  construction. 

The  life  of  a  motor  system  depends,  above  all,  upon  good  com- 
mutation. The  doubt  as  to  the  possibility  of  satisfactory  commuta- 
tion was  the  main  cause  why  the  value  of  the  commutator  motor 
and  its  adaptability  to  alternating-current  did  not  receive  appre- 
ciation. In  the  second  place  should  be  considered  the  capacity  to 
develop  sufficient  torque  at  a  moderate  speed  and  with  as  high  a 
power  factor  as  possible.  There  are  systems,  as  will  be  shown,  which 
are  far  superior  in  this  respect  to  the  alternating-current  series 
motor,  and  which  also  in  comparison  with  the  direct-current  motor 

[370J 


DERI:     SINGLE-PHASE  MOTORS. 


377 


leave  little  to  be  desired.  Such  machines,  which  can  be  designated 
collectively  under  the  name  "  Induction  motors  with  commutators," 
have  two  fields,  one  of  which  induces  the  energy  current,  which  in 
connection  with  the  other  field,  according  to  phase  and  space  rela- 
tion, produces  the  torque. 

The  generation  of  power  currents  by  induction  (transformation) 
presents  the  great  advantage  that  the  machines  can  receive  high 
tension  directly;  furthermore,  there  follows  the  consequence,  im- 
portant in  many  respects,  that  the  commutation  takes  place  in  the 
secondary  circuit,  i.  e.,  the  low-tension  circuit. 

The  following  observations  are  based  upon  the  two  types  of 
series  motors:  First,  the  usual  arrangement  shown  in  Fig.  1,  in 
which  the  armature  with  commutator  and  the  magnetic  field  are 
connected  in  series  across  the  line  as  in  the  series  direct-current 
motor;  and,  secondly,  the  arrangement  shown  in  Fig.  2,  in  which 


Flg.1 


Fig.  2 


the  armature  carrying  the  induced  currents  and  the  stator  winding 
producing  the  field  are  connected  in  series,  and  short-circuited, 
form  a  closed  secondary  circuit. 

In  the  first  type,  in  which  primary  currents  are  commutated 
(Fig.  1),  the  self-induction  of  the  armature  is  eliminated,  for 
example,  by  a  short-circuited  winding  on  the  stator,  and  which  lies 
in  the  axis  I  of  the  brushes. 

In  Fig.  2  a  transformer  is  combined  with  a  motor.  F^  is  the 
flux  of  the  transformer,  which  the  stator  winding,  I,  constitutes 
with  the  armature,  the  former  being  connected  to  the  main  circuit. 
The  brushes  are  short-circuited  around  the  stator  II  so  that  the 
power  currents  in  the  armature  produce  the  flux  F2.  This  latter 
field  is  actually  the  real  field  of  the  motor,  because  it  lies  in 
quadrature  with  the  power  currents  and  in  conjunction  with  them 


378  DERI:     SINGLE-PHASE  MOTORS. 

develops  the  torque.  The  motor  is  in  the  secondary  circuit,  and 
only  secondary  currents  are  commutated,  and  the  potential  across 
the  brushes  in  the  direction  of  the  axis,  I,  can  be  established  with 
any  desired  ratio  of  pressure  reduction.  (In  the  deductions  which 
fellow,  for  the  sake  of  simplicity,  the  ratio  is  assumed  as  1  to  1). 

The  triangle  of  e.m.f's.  —  Fig.  3  —  shows  the  relation  between 
the  several  quantities  in  the  series  motor,  ab  represents  the  line 
potential  with  respect  to  phase  and  amount  or  the  e.m.f.  (E)  be- 
tween the  brushes  induced  by  the  field,  F±.  The  phase  of  the 
transformer  flux,  Flt  whose  amount  is  measured  by  be  or  ab  respect- 
ively, lies  at  right  angles  to  these  vectors,  and  for  the  primary  series 
motor  in  the  direction  ad,  and  for  the  secondary  series  motor  in  the 
direction  ad2. 

In  both  cases  F2  is  excited  by  the  armature  current  (power  cur- 
rent /),  F2  and  I  are,  therefoi-e,  always  in  phase.  At  any  speed  n, 
expressed  as  a  fraction  of  synchronous  speed,  the  e.m.f.,  E  a,  in- 
duced in  the  armature,  as  a  result  of  rotation  in  the  field  F2)  is  in 
phase  with  this  flux  and,  therefore,  also  in  phase  with  the  power 
current  producing  this  flux.  This  e.m.f.  be  is  so  represented  that 
the  exciting  potential  Em,  i.  e.,  the  potential  necessary  to  er- 
cite  the  flux  F2)  is  at  right  angles  to  the  phase  of  the  current  ac. 

In  the  phase  direction  be  is  also  found  the  ohmic  drop  Ir.  The 
magnitude  of  this  drop,  which  is  of  little  importance  in  the  relation 
and  phase  of  the  working  quantities,  as  also  the  potential  in  the 
direction  ~bc  which  is  necessary  to  excite  the  stray  field,  will  be  left 
out  of  consideration  in  order  not  to  render  difficult  the  considera- 
tion of  the  general  questions.  These  omitted  quantities  can  be 
considered  later,  in  the  well-known  way,  in  calculating  the  effi- 
ciency, temperature  rise,  etc.,  etc. 

The  triangle  abc  is  the  diagram  of  the  series  motor,  and  with  its 
aid  all  the  quantities  involved  can  be  deduced.  In  this  diagram 
the  phase  angle  £  assumes  particular  importance,  not  only  for 
the  determination  of  the  power  factor,  but  also  to  indicate  the 
relation  between  the  various  quantities  involved. 

J^  :  =  Fc,  or:  ^  ~al\  F*  :  ^  a~c',  I:  -£?  ac 
Z/  Zi  Zt  Z/2 

The  sign  :  is  that  of  proportionality;  Z1  and  Z2  the  respective 
number  of  turns,  although  not  variable,  are  given  in  order  to  indi- 


DERI:     SINGLE-PHASE  MOTORS.  379 

cate  the  dependence  of  the  flux  upon  them.  The  same  is  true  of 
the  magnetic  resistance  p,  which  is  only  slightly  variable  between 
practical  limits.  The  length  ac  is,  therefore,  the  measure  of  both 
the  flux  F2  and  approximately  also  of  the  current  I,  the  phase  di- 
rections of  both  falling  in  be. 

The  torque  T:-^  ~a~c 

-^2 

The  speed   n:  (^-}-^- 
V  A  /  a  c 

The  actual  power  output  of  the  motor  P  :  [ -~-o-  )'a 

Y*"/ 

The  internal  power  factor  cos  § :  fa. 

Making  ab  =  E  and  expressing  above  quantities  as  functions  of 
the  angle  fl, 

/  :  E  sin  <j;  T  :  E2  sin2  <?;  P  :  E2  sin  $  POS  <j,  and  n  :  cotg  <j. 

The  apparent  power  output  EX  I  :  E~  sin  $m 

If  we  project  7  on  ~abf  according  to  the  above  for  E  =  ab  =  l, 

P\~cg\  EXl'-ac;  T\~ag. 

In  Fig.  4  the  quantities  T,  P  and  cos  8  are  constructed  as  func- 
tions of  the  speed,  as  n  :  cot  d,  referred  to  a  constant  sin  <j,  is 
used  as  the  axis  of  abscissae.  It  appears  clearly,  from  these  curves, 
how  rapidly  T  diminishes  with  increasing  speed.  In  the  case  of 
the  primary  motor  d  =  <p.  In  the  case  of  the  secondary  series 
motor,  it  is  necessary  also  to  know  the  phase  of  the  primary  cur- 
rent. For  this  purpose  we  proceed  according  to  Fig.  5  as  follows : 

The  magnetizing  current  of  the  field  F,  in  relation  to  the  num- 

Iser  of  effective  armature  turns  Z^  is  i   :-^  aby    its  phase  is  at 
Z\ 

right  angles  to  ab.     If  we  lay  down  this  constant  value,  in  the 

~fo  

ratio  .-=.  then  ccl  becomes  the  component  of  pressure  by  which  the 

ac 

phase  of  the  primary  current  be1  is  determined.  The  difference  in 
phase  between  the  primary  and  secondary  currents  is  <pv  and 
<»os  y  =  cos  .(<?  -f-  ^±)  is  the  external  power  factor  of  the  system. 

The  magnitude  of  cc1  is  proportional  to  cot  d  and  consequently 
to  n.  Similarly  as  in  Fig.  1,  referring  to  sin  $  as  constant,  we 
•obtain  the  geometric  locus  of  the  points  c1  as  a  curve  which  at 
first  gradually  diverges  from  the  circular  arc  in  going  from  ~fy 
vtoward  a,  then  rapidly  diverges  and  finally  becomes  assymptotic 


380 


DERI:     SINGLE-PHASE  MOTORS. 


to  ad.  The  point  of  counter  curvature  of  this  curve  corresponds 
to  the  values  of  9  and  n  at  which  cos  <p  is  a  maximum. 

In  the  secondary  series  motor  cos  y—1  cannot  be  reached; 
cos  <p>  in  the  case  of  primary  and  cos  $  in  the  case  of  the  secondary 
motor  can  only  approach  the  value  unity  in  the  case  of  an  ideal 
no-load  operation. 

As  regards  the  process  of  commutation,  we  shall  investigate 
in  addition  to  the  so-called  reactance  voltage,  also  the  e.m.f  s.  in- 


duced in  the  short-circuited  turns  by  the  fluxes  F±  and  F2.  These 
e.m.f's.  are  usually  of  a  higher  order,  quantitatively,  than  the  re- 
actance voltage  produced  by  the  variation  of  contact  between 
brush  and  commutator  for  the  latter,  as  in  the  case  of  direct-cur- 
rent machines,  is  determined  only  by  the  stray  field  which  is  inter- 
1  inked  with  the  short-circuited  turns,  while  the  former  are  due  to 
the  total  flux.  The  coil,  short-circuited  during  commutation,  is 
interlinked  with  the  flux  F2  and  at  the  same  time  cuts  the  field 


DERI:     SINGLE-PHASE  MOTORS.  381 

flux  FI  in  its  densest  zone  with  a  speed  corresponding  to  n.  There 
are,  therefore,  induced  in  the  coil  two  different  e.m.f's.  both  of  the 
same  frequency:  i.  e.,  e\\  F2  independent  of  the  speed,  proportional 
to  F2,  with  the  phase  of  which  it  is  in  quadrature ;  and  the  ec  :  nFlt 
proportional  to  the  speed  and  to  F±  and  in  phase  with  Ft. 

The  diagram  of  these  e.m.f  s.  can  be  derived  directly  from  the 
e.m.f.  triangle  Fig.  3,  as  shown  in  Fig.  6. 

Let  ab  represent  the  measure  of  the  e.m.f.  e^  corresponding  to 
F2  maximum  and  for  a  certain  speed  n :  cotg  S.  Draw  the  triangle 
abc.  The  phase  direction  of  F2  is  for,  ^  is  at  right  angles  to  it  and 
proportional  to  F2  and  hence  determined  by  ^T  in  dimension  and 
phase.  The  magnitude  of  e0  in  the  direction  of  Fv  is  ^#,  at  the 
speed  n  for  instance. 

£5 

For   the   primary  series   motor   adl :  -==-     for   the   secondary 

ac 

ad2  =  =•  .     The  resultant  e0  of  the  e.m.f  s.  is  cdl  or  cd2  re- 

ac 
spectively. 

As  far  as  the  reactance  voltage  er  is  concerned,  its  phase  co- 
incides with  the  current  phase,  being  in  the  direction  be,  and 
quantitatively  r  :  nl :  E&  (on  a  scale  approximately  0.1  —  0.2 
bo ) .  From  the  diagram  it  appears  that  in  the  case  of  the  primary 
motor,  er  and  eQ  are  always  at  right  angles  to  each  other,  whereas 
ir.  the  case  of  the  secondary  motor  the  obtuse  phase  angle  is 
variable  and  only  at  practicable  speeds  er  and  e0  are  opposed  to 
one  another.  In  the  case  of  the  secondary  commutation  we,  there- 
fore, arrive  at  an  advantageous  compensation  of  the  reactance. 
The  result  of  all  three  e.m.f  s.  in  the  short-circuited  winding,  e 
measured  by  ^/x  or^2  respectively  must  be  considered  in  the  com- 
mutation as  the  cause  of  sparking. 

In  Fig.  6  curves  of  e  are  shown  for  both  methods  of  connecting 
the  series  motor.  One  sees  that  e  in  the  case  of  the  primary  series 
motor  (e^)  deviates  but  little  from  its  initial  value,  and  increases 
at  greater  speeds.  In  the  case  of  the  secondary  series  motor,  on 
the  contrary  e2  falls  considerably  below  its  initial  value  and  is  a 
minimum  at  a  speed  which  lies  within  the  limits  of  the  usual 
operating  speeds.  The  latter,  therefore,  commutates  considerably 
better  than  the  primary  motor  in  which  good  commutation  is  out 
of  the  question. 

We  shall  investigate  in  a  similar  way  the  repulsion  motor  in 


382 


DERI:     SINGLE-PHASE  MOTORS. 


Fig.  7.  The  stator  winding  is  connected  to  the  line  and  the  brushes, 
inclined  to  the  axis  Y  at  an  angle  a,  are  short-circuited.  The 
brush  axis  is  indicated  as  X.  We  shall  not  proceed  with  the  in- 
vestigation of  the  operation  of  this  motor  according  to  the  method 
usually  followed  of  resolving  the  fields,  e.m.f's.  and  ampere-turns 
into  components  as  functions  of  sine  and  cosine  a,  but  we  shall  pro- 
coed  in  other  ways  which  are  simpler  and  unobjectionable. 

We  may  proceed  in  two  ways:  According  to  Fig.  8,  we  can 
divide  the  stator  winding,  which  we  may  assume  as  uniformly 
distributed  over  the  circumference  of  a  closed  stator,  into  two 
groups  connected  in  series  with  the  same  current  flowing  through 
them  and  which  exert  and  are  subjected  to  the  same  effect  as  the  com- 
bined system.  The  four  groups  of  windings  on  the  stator,  as  shown 


in  the  figure,  are  so  connected  as  to  produce,  by  the  current  flowing 
in  all  of  them,  the  flux  in  the  direction  of  the  arrow,  and  to 
gmerate  the  field  with  the  axis  Y.  In  the  distribution  of  the  lines 
of  force  and  the  amount  of  magnetizing  current,  there  must  be 
taken  into  account,  in  addition  to  the  magnetic  resistance  of  the 
entire  flux,  the  reaction  of  that  part  of  the  armature  circuit  which 
is  short-circuited  between  the  brushes.  None  of  the  effects  suffer 
any  change  if  we  consider,  as  connected  in  the  order  shown,  the 
ampere-turns  /  whose  axis  coincides  with  X,  and  the  ampere-turns 
II,  whose  axis  is  perpendicular  to  X.  Only  the  sequence  of  the 
single  elements  in  the  series  has  been  changed,  which  is  without  any 
importance  on  the  result.  We  have,  therefore,  two  stator  windings 
7  and  11,  in  general  with  different  number  of  turns  and  also  of 
different  magnetic  resistance,  and  the  arc  covered  by. the  windings 
and  the  polar  arc  are  unequal.  The  axis  of  the  two  windings  are 
perpendicular  to  each  other.  We  can,  therefore,  construct  the 
diagram  Fig.  9. 


DERI:     SINGLE-PHASE  MOTORS. 


383 


We  can  proceed  in  another  way  in  accordance  with  Fig.  10. 
in  accordance  therewith,  the  armature  winding  is  divided  into 
four  groups  which  are  connected  in  pairs  7  and  /,  then  II  and  II 
in  parallel,  and  the  two  pairs  connected  in  series  are  closed  on 


Fig.  10 


Fig.  9 


themselves.  The  division  is  such  that  the  groups  connected  to- 
gether when  traversed  by  the  current  produce  the  same  magnetic 
field  in  the  direction  of  the  arrows  and  corresponding  with  the 
brush  axis  X,  as  would  the  entire  armature  winding  when  short- 
circuited  through  the  brushes.  It  appears,  therefore,  that  the 
armature  phenomena  are  as  follows:  In  winding  I  an  e.m.f  is 


Fig.  11 


induced  by  the  coaxial  stator  winding,  which  e.m.f.  is  equal  to 
that  of  the  entire  armature;  winding  I  forms  a  circuit  closed 
through  winding  II,  hence  excites  a  flux  in  the  latter  which  is 
free  from  any  armature  reaction.  The  diagram  of  this  arrange- 
ment, in  accordance  with  the  foregoing  analysis,  is  shown  in  Fig.  11. 
This  diagram  differs  from  the  arrangement  shown  in  Fig.  2  in 
that  the  winding  exciting  the  field  is  not  on  the  stator  but  on  the 


3S4  DERI:     SINGLE-PHASE  MOTORS. 

lotor.  WhetHer  the  armature  rotates  in  a  field  excited  by  fixed 
stator  windings  or  by  rotor  windings  amounts  to  the  same  inducing 
effect,  provided  only  that  in  the  latter  case  the  axis  of  the  exciting 
windings  is  held  fixed  by  brushes. 

According  to  the  first  arrangement  the  coils  I  are  the  inducing 
v;inding,  and  according  to  the  second  they  are  the  induced 
winding  ;  the  coils  11,  however,  on  account  of  being  at  right  angles 
tc  X  or  Y,  respectively,  can  neither  exert  nor  receive  any  induction. 

The  ratio  of  the  number  of  turns    •—  is  -  :^  ;  the  ratio  of  the 

Za  a 

poles  faces  the  reciprocal  ___^i__.     This  alone  sufficiently  indi- 

900_  a 

cates  the  importance  of  the  brush  position,  represented  by  the  angle 
«  and  its  effect  on  the  flux,  torque,  etc.  It  appears  also  that  by 
a  variation  of  this  angle  by  turning  the  brushes,  all  of  the  secondary 
quantities  and  their  functions  can  be  varied. 

In  Fig.  12  the  armature  current  I  in  amount  and  phase  is  de- 
termined graphically  by  the  following  considerations: 

abc'  is  the  diagram  of  the  primary  pressures,  ^  the  terminal 
pressure,  ^'  the  e.m.f.  of  the  armature  and  also  the  pressure  of 
the  stator  winding  I,  and  ac1  that  of  the  stator  winding  II.  F^  is 
proportional  to  ^c7  and  in  the  direction  JJJ1  ;  the  same  is  true  of  i. 
The  component  of  the  armature  e.m.f.  which,  induced  by  the  com- 
ponents F2,  belonging  to  the  exciting  current,  it  is  proportional  to 

gJS 

F%  and  to  n  :      —    and  can  be  measured  by  C(/.    Then  frc  is  the 
etc 

component  of  the  armature  e.m.f.  belonging  to  the  exciting  current 
/  and,  therefore,  also  the  direction  of  7.  The  angle  <pl  lying  be- 
tween be  and  fo  indicates  the  phase  difference  between  primary  and 
secondary  current.  If  we  prolong  ^  until  it  cuts  the  circle  in  I 
and  we  draw  through  I  the  line  ^  until  it  cuts  ^7  prolonged,  then, 


owing  to  the  equality  of  the  angles,  ^  =       ,   a<'  ;  am  is,  therefore, 

the  measure  of  I,  which  is  parallel  and  equal  to  ^  produces 
the  right-angled  triangle  ~fod  similar  to  #,/#.  The  first  is 
the  diagram  of  the  e.m.fs  corresponding  to  the  current  7. 
The  connection  ^  can  be  proven  to  be  always  perpendicular  to  ~^ 

and,   ad  :  n  (g-  \  ~^  t  ~fo  and  ^  are  the   quantities   which   are   a 


DERI:     SINGLE-PHASE  MOTORS. 


38r, 


measure  of  the  torque  and  capacity  because  they  depend  on  the 
armature  current  and  on  the  component  of  the  field  which  is  in 
same  phase  with  it. 

We  are  obviously  led  to  the  same  result  if  in  investigation  of  the 
repulsion  motor  we  proceed  according  to  Figs.  10  and  11.  The 
following  consideration  is  much  simpler  than  the  foregoing  and 
leads  directly  to  the  diagram  of  Fig.  13. 

This  is  also  the  proof  and  confirmation  of  the  result  of  the  pre- 
vious deductions.  In  this  case  the  internal  circuit  consists  of  the  two 
rotor  windings  I  and  IT.  In  winding  I  the  e.m.f  E :  ab  is  induced 
by  a  constant  Fr  On  rotating  the  armature  the  winding  I  cuts 
the  flux  II,  and  winding  II  the  flux  7.  The  e.m.f  "s.  induced  as  a 
result  of  the  rotation  have  the  phase  direction  of  the  inducing  fields. 
E&  .  ~bc  is  of  the  same  phase  as  7;  the  e.m.f.  in  winding  77  Ek  is  at 
right  angles  to  ab. 

Ek  :  «5  :  nZ*F:  n 

The  polygon  of  e.m.f's.  is  abcda  in  which   ad  is  a  compensating 
e.m.f.  proportional  to  the  speed,  adding  itself  geometrically  to  the 
line  pressure. 
We  can  indicate  the  important  quantities  by  Fig.  14,  by  con- 


Flfl.  15 


structing  a(f  :  n  perpendicular  to  ^j,  drawing  the  semi-circle  around 
fo£,  and  determining  the  point  "^  according  to  n  :  cot  9  .  The 
quantities  fa,  cd  an^  also  cd  and  ^  will  vary  in  the  ratio 

1 :  |/  1  +  n2  (— )        2'  and  P  will  also  increase  with  corresponding 

coefficients.  The  output  of  the  repulsion  motor  will  be  as  great 
as  corresponds  to  the  line  pressure,  and  consequently  at  a  given 

ELEC.  RYS. 25. 


386  DERI:     SINGLE-PHASE  MOTORS. 

speed  as  great  as  in  the  case  of  the  primary  and  greater  than  in  the 
case  of  the  secondary  series  motor. 

Since  the  compensating  e.m.f.  furnishes  a  part  of  the  field  ex- 
citation, it  is  necessary  to  provide  a  less  number  of  ampere-turns 

externally  in  the  ratio  ~.  as  shown  in  Fig.  14.    It  can  be  shown  that 

r.d 

~ac  =  bd  sin  (  d  —  ^x)  while  7d  =  ^  sin  £  .  For  small  values  of  <J 
in  which  ^  still  has  a  considerable  value.  ^  may  become  small. 

In  addition,  the  compensating  effect  of  ~ad  is  manifested  by  the 
fact  that  the  phase  difference  between  the  power  current  and  the 
e.m.f.  is  diminished  by  the  angle  <f>±.  The  phase  shifting  which 
takes  place  in  the  transformer  7  is  to  a  certain  extent  balanced 
by  the  compensation.  Cos  <f>  will  be  about  the  same  as  in  the 
case  of  the  primary  series  motor  and  will,  therefore,  approach 
closer  to  the  maximum  value  than  in  the  case  of  the  secondary 
series  motor. 

The  commutation  phenomena  in  the  case  of  the  repulsion  motor 
can  be  represented  by  consideration  similar  to  the  foregoing,  taking 
into  account,  however,  that  the  e.m.fs.  ^  and  eo  are  induced  by 
those  fluxes,  which,  according  to  the  analysis  of  Fig.  9,  correspond 
to  the  number  of  turns  Z^  and  Z2.  Therefore  Fig.  14  shows  also 
on  the  proper  scale  the  diagram  of  e.m.fs.  in  the  short-circuited 
winding.  In  amount  and  phase  direction  e^  ^  ec  :  ad  an^ 
eo :  7w;  ao  ig>  therefore,  the  e.m.f.,  e,  resultant  of  all  three. 

ad  is  proportional  to  the  speed.  We  can,  therefore,  project  the 
values  of  c  as  ordinates  upon  n.  The  curve  shows  the  dependence 
of  e  upon  n.  e  is,  therefore,  a  maximum  at  starting  (just  as  in 
the  case  of  the  series  motor  e:ab),  diminishes  rapidly,  however, 
with  increasing  speed  and  reaches  at  a  certain  speed  a  minimum, 
which  is  less  than  the  reactance  voltage. 

The  compensating  e.m.f.  of  the  repulsion  motor  depends  upon  the 

ratio  --,  hence  upon      Oa    _.     On  the  other  hand,  the  torque  and 


energy  of  this  motor  is  inversely  proportional  to  the  number  of 
turns,  i.  e.,  inversely  proportional  to  Z2  or  to  higher  powers  of  Z.2. 
Herein  lies  the  weakness  of  the  ordinary  repulsion  motor.  It  is 
not  at  all  sufficient,  as  was  originally  believed,  to  shift  the  brushes 

by  45  deg.  (i.  e.,  one  quarter  of  the  polar  distance),  which  would 

17 
correspond  to  the  ratio  —1=1.    The  e.m.f.  induced  while  at  rest 


DERI:     UINGLti-PHAtiE  MOTORS.  387 

in  the  winding  /  would  be  barely  sufficient  to  excite  the  field 
F2=Fi  with  the  current  I  =  i.  The  maximum  power  current 
would  be  t,  hence  the  starting  power  too  small  and  the  output 
insufficient.  Consequently  it  is  necessary  to  make  the  angle  a 
much  less  than  45  deg.  in  order  to  obtain  sufficient  torque.  In  re- 
ality the  angle  is  chosen  at  about  25  deg.  to  20  deg.,  corresponding 

yr 

to  a  value  —  =0.40  to  0.30.     In  order,  therefore,  to  obtain  a 

Zi 
greater  output  one  sacrifices  a  part  of  the  compensating  effect. 

The  repulsion  motor  is,  nevertheless,  a  very  useful  machine, 
particularly  if  the  windings  are  carried  out  in  two  parts,  as  shown 
in  the  diagram,  Fig.  9.  WJth  the  aid  of  a  switching  arrangement, 
reversal  of  direction  and  control  is  easily  made  by  the  inversion  and 
variation  of  the  field  of  force.  Another  and  more  convenient 

method  for  the  reversal  and  control  within  the  widest  limits  con- 

g 
sists  in  varying  the  ratio  •-?  by  shifting  the  brushes.    In  order  to 

Zi 

obtain  the  maximum  output,  it  would  be  necessary  to  make  «  so 
small  that  it  would  embrace  only  two  to  three  commutator  bars, 
which  would,  however,  make  the  motor  unreliable  in  operation  and 
commutation.  On  this  account  the  output  of  the  repulsion  motor 
is  limited;  in  other  words,  dependent  upon  the  number  of  the 
commutator  bars  and  the  size  of  the  commutator. 

We  will  now  refer  to  an  arrangement  devised  by  the  author  ac- 
cording to  Fig.  15,  in  which  all  of  the  characteristics  of  the  re- 
pulsion motor  are  left  substantially  undisturbed,  permitting,  how- 
ever, the  angle  a  to  be  made  twice  as  large  as  with  the  usual  arrange- 
ment. One  pair  of  brushes  is  placed  in  the  Y  axis  and  another 
pair  at  the  angle  in  the  V  axis.  The  two  pairs  of  brushes  are  con- 
nected as  shown,  so  that  they  embrace  the  obtuse/  angle  (180  —  «). 
The  effect  of  this  arrangement  can  be  judged  if  one  imagines  an 
armature  in  the  Y  axis  connected,  as  shown  in  series  and  in  closed 

circuit  with  another  armature  in  the  V  axis.     The  ratio  off  the 

& 
number  of  turns  —  ?  in  accordance  with  the  diagrammatic  analysis 


is  in  this  case  7^-^  —     If  this  ratio  and  the  resulting  output  are 

loO  * 

to  be  of  the  same  v 
The  brushes  have  to  carry  the  same  load  in  this  arrangement  as 


388 


DERI:     SINGLE-PHASE  MOTORS. 


in  the  case  of  the  ordinary  repulsion  motor  with  the  same  power 
current  and  cross-section  of  all  brushes.  The  number  of  brushes 
need  not  be  increased  if  with  the  proper  winding  of  the  armature 
fewer  brushes  are  used  than  the  number  of  poles,  .for  instance,  for 
eight  poles,  two  positive  and  two  negative  poles  have  two  brushes 
each. 

This  arrangement  is  particularly  adapted  to  controlling  by 
brush  shifting,  perhaps  by  shifting  the  V  brushes  alone.  Accord- 
ing to  the  above  presentation  a  compensating  effect  is  obtained 
either  by  exciting  the  field  by  primary  current,  one  component  of 
which  is  the  magnetizing  current  for  the  flux  F±9  or  by  placing  the 
windings  which  excite  the  field  and  wljich  are  a  part  of  the  main 
circuit  on  the  armature  and  subjecting  them  to  induction  by  Fr 

Both  of  these  causes  of  the  compensating  effect  are  contained  in 
the  arrangement  of  Fig.  16,  which  shows  the  so-called  compen- 


Flg.  16 


Fig.  17 


sated  motor  of  the  Union  Elektrizitats-Gesellschaft.  The  brushes 
in  the  axis  /  are  short-circuited.  The  diagonal  brushes  in  this  axis 
II  are  traversed,  on  account  of  the  series  connection  with  the  stator, 
by  the  main  current,  either  directly  or  at  a  transformed  potential 
through  the  insertion  of  a  transformer.  The  armature  carries  the 
power  current  in  short-circuit  and  rotates  in  the  field  of  force 
excited  by  the  primary  current  in  the  armature  betAveen  the  diag- 
onal brushes. 

.  The  actions  in  the  two  axes  of  the  armature  do  not  interfere 
with  one  another  notwithstanding  that  they  occur  in  a  common 
winding,  because  the  axes  lines  are  in  neutral  positions  relatively 
to  each  other.  Considering  that  the  axes  are  held  fast  in  the 
armature  by  the  brushes,  the  arrangement  can  also  be  represented 
by  the  diagram  of  Fig.  17. 

The  diagram  of  the  working  current  is  similar  to  that  of  the 
repulsion   motor. 


DERI:     SINGLE-PHASE  MOTORS. 


380 


Fig.  18  shows  the  polygon  of  e.m.f  s.  abcda  with  relation  to  the 
working  current.  The  e.m.f.  of  the  armature  coil  I,  which  is  re- 
flected in  the  stator  winding,  is  made  up  of  E&:bc"  and  E0:ak. 
These  e.m.f's.  are  generated  by  the  rotation  of  the  coil  in  the  two 
components  of  the  field  F2,  one  of  which  is  excited  by  I,  the  other 
by  i.  The  e.m.f.,  En  :  kd,  is  induced  in  the  armature  coil  II  on 
account  of  its  rotation  in  the  field  F^ ;  on  the  other  hand,  Em :  ac" 
is  consumed  in  exciting  the  field  of  force  and  the  stray  field.  E0 
and  En  have  the  direction  ad;  db  and  bd  form  the  angle  ?. 

In  order  to  construct  the  diagram,  with  relation  to  the  working 

—  —  /%\— 

current,  ad  is  drawn  at  right  angles  to  ab  (ad:  tan  r:n\~7~)  <*&)• 

On  bd  as  the  total  useful  e.m.f.,  the  work  polygon  is  constructed 
for  n :  cot  d ,  in  which  all  quantities  ad,  be  and  cd  are  referred  to 


the  phase  and  amount  of  the  working  current  I.  Not  only  is 
the  phase  displacement  and  the  drop  in  voltage  caused  by  the  trans- 
formation, compensated  for  in  this  way,  but  the  primary  diagram 
also  receives  a  favorable  displacement. 

On  the  assumption  of  the  direct  connection  in  series  between 
the  stator  winding  and  exciting  winding,  ok  and  led  are  equal  in 
amount,  ad :  tan  y  is,  therefore,  twice  as  large,  and  the  compen- 
sating effect  more  powerful  in  the  same  proportion  than  in  the 
repulsion  motor,  be'  shows  the  direction  of  the  primary  current; 
ac'  is  the  measure  of  the  exciting  e.m.f.  to  be  supplied  externally. 

By  the  insertion  of  the  series  transformer  the  compensation  can 

<7 

be  varied  together  with  the  ratio  —     Still  greater  is  the  variation  if 


390  DERI:     SINGLE-PHASE  MOTORS. 

with  the  aid  of  a  potential  regulator  the  number  of  turns  in  both 
be  varied  simultaneously  in  opposite  directions. 

The  example  in  Fig.  19  shows  the  stronger  influence  of  ad  upon 
cos  d,  T  and  P.  One  can  see  that  cos  <p  approaches  the  value  of 
unity  more  rapidly  than  in  the  case  of  the  repulsion  motor,  and 
becomes  unity  at  a  practicable  speed. 

The  exciting  voltage  ac1  which  is  supplied  externally  diminishes 
rapidly  in  this  arrangement  and  can  reach  zero,  in  which  case  the 
field  excitation  is  accomplished  by  the  compensating  e.m.f.  alone. 

As  for  the  commutation,  it  is  necessary  to  judge  the  performance 
of  the  brushes  in  the  axis  I  carrying  the  working  current,  in  a  way 
similar  to  that  of  the  repulsion  motor,  but  the  fundamentally 
different  phenomena  which  takes  place  in  connection  with  the 
exciter  brushes  must  be  investigated  from  a  special  point  of  view. 
Fig.  19,  which  shows  the  e  curve  for  the  brushes  carrying  the 
working  current  indicates  that  the  commutation  at  normal  speed 
is  favorable ;  on  starting,  however,  and  at  low  speeds  the  same  diffi- 
culties exist  as  in  the  case  of  the  repulsion  and  series  motors.  In 
order  to  judge  of  the  performance  of  the  exciter  brushes,  we 
'have  to  consider  that  the  turns  short-circuited  by  these  brushes 
are  part  of  a  winding  which  is  already  short-circuited  by  the  brushes 
in  the  axis  /.  The  latter  short-circuiting  with  full  contact  of  the 
brushes  can  be  considered  as  constant  in  comparison  with  the  very 
variable  short-circuiting  of  the  individual  turns  by  the  leading 
and  trailing  brushes.  The  pressure  diagram  of  the  armature  (bcmb 
in  Fig.  18)  is  composed  of  the  e.m.f  s.  induced  by  F1  and  gener- 
ated as  a  result  of  the  rotation  in  the  entire  field  of  force,  and 
also  of  the  small  ^  which  represents  the  exciting  e.m.l  for  the 
stray  field  in  the  armature.  The  same  relations  hold  also  for  the 
e.m.fs.  in  the  commutating  coil,  which  are  induced  under  similar 
conditions  as  the  whole  armature  winding  in  the  axis  7.  Only  the 
scale  of  the  vectors  is  different  in  the  ratio  of  the  number  of  turns 
and  the  local  distribution  of  the  field  of  force  (about  in  the  ratio 

*_Z«V 

8  Z^  }' 

During  the  period  of  commutation  the  e.m.f.,  JJJ,  exciting  the 
stray  field,  and,  therefore,  the  exciting  current,  will  vary  but  little. 
In  addition  there  will  appear  a  small  reactance  pressure.  The  lat- 
ter is  unimportant  in  the  production  of  sparking,  because  the  ex- 
citing current,  which  varies  with  the  contact  of  the  brushes  II, 


DERI :     SINGLE-PHASE  MOTORS.  391 

svhich  as  a  rule  is  weaker  than  the  working  current,  finds  an 
equalizing  shunt  circuit  in  the  short-circuited  connection  of  the 
brushes  /.  The  influence  of  the  residual  e.m.f.,  e,  on  the  commu- 
tation is  doubtless  small.  The  commutation  under  the  exciting 
brushes  proceeds  without  difficulty  and  requires  no  special  care  or 
consideration. 

The  so-called  compensated  single-phase  motor  represents  on  the 
whole  an  improved  repulsion  motor.  In  comparison  it  shows,  how- 
ever, some  disadvantages,  because  in  addition  to  the  double  system 
of  brushes,  a  special  transformer  for  excitation  and  special  arrange- 
ments for  regulation  are  necessary. 

If  we  wish  to  investigate  in  the  same  manner  the  ordinary  single- 
phase  induction  motor  having  a  squirrel  cage  armature  and  no 
commutator,  we  recognize  an  analogy  with  the  previously  described 
arrangements  which  becomes  more  complete  when  we  consider  both 
pairs  of  brushes  as  separated  from  the  stator  circuit,  and  each 
pair  as  short-circuited  on  itself,  as  indicated  in  diagram,  Fig.  20. 

In  order  to  proceed  from  this  arrangement  to  the  induction 
motor,  it  is  only  necessary  to  imagine  instead  of  the  armature 
short-circuited  by  the  brushes  in  two  diagonal  directions,  two 
diagonally-placed  short-circuited  coils,  or  as  a  further  simplifica- 
tion a  single  short-circuited  coil  effective  in  both  directions. 

The  diagram  of  e.m.f's.  is  shown  in  Fig.  21.  In  the  axis  7,  the 
<\m.f.  ^  is  produced  by  the  line  voltage  or  Flm  There  will  be  in- 
duced an  e.m.f.  ~^  in  the  axis  II  in  proportion  to  the  speed  and  in 
phase  with  the  generating  flux  I,  hence  at  right  angles  to  ab.  The 
currents  corresponding  thereto  excite  a  cross-flux  which  penetrates 
through  the  rotor  and  stator.  These  magnetizing  currents  as  well 
ay  the  cross-flux  F2  excited  by  them  have  the  direction  ^/. 

The  direction  ^df  diverges  but  little  from  ~~^  (in  contradistinction 
to  the  previous  treatment,  this  acute  angle  cannot  be  neglected, 
nor  can  the  ohmic  drop,  because  both  are  important  working  factors 
of  this  motor).  Having  the  same  phase  direction,  there  is  gener- 
ated in  the  axis  7  of  the  armature  winding  at  a  certain  speed,  an 
c.Tn.f.  "^  in  phase  with  F2  and  proportional  to  n2.  Out  of  the  re- 
sultant e.m.f.  T^f,  there  appear  the  ohmic  drop^  and  at  right  angles 
thereto  the  e.m.f.  ^f  exciting  the  stray  field  in  the  armature. 
7 :  ^f  the  phase  of  the  working  current  is  ~fif  F2 :  n  „&  the  phase 
of  thp  field  ^  The  angle  ft  between  the  direction  of  these 
two  phases,  whose  cosine  is  a  measure  of  T,  will  be  disadvantage- 


392 


DERI:     SINGLE-PHASE  MOTORS. 


ously  large  with  the  exception  of  small  values  of  ef  near  to  synchron- 
ism. The  same  is  true  in  reference  to  <f>,  which  is  greater  by  (^i-hr) 
than  the  angle  previously  referred  to.  The  power  factor  will  be 
poor  between  rest  and  a  speed  slightly  under  synchronism.  The 
motor  can,  therefore,  operate  advantageously  only  at  nearly  syn- 
chronous speed,  but  even  then  only  with  limited  output,  because  at 
this  speed  a  small  e.m.f.  ~^e  remains,  and  the  working  current  is, 
therefore,  weak.  The  triangle  a1  frc1  shows  the  work  diagram  of 
the  induction  motor  and  contains  the  quantities  T,  P  and  cos  <J. 
These  considerations  confirm  the  well-known  fact  that  the  induc- 
tion motor  without  commutator  for  single-phase  current  is  an  un- 
desirable machine  —  quite  independent  of  the  fact  that  it  has  no 


Fig.  20 


Fig.  22 


Fig.  23 


starting  torque,  so  as  to  start  itself,  and  because  it  admits  of  no 
external  control  on  account  of  its  being  exclusively  self -exciting. 

As  an  appendix  to  these  considerations  the  author  submits  his 
arrangement  which  shows  the  application  of  the  commutator  and 
the  externally  excited  field  in  combination  with  the  closed  circuit 
armature. 

Fig.  22  is  the  diagrammatic  representation  of  this  motor  and 
Fig.  23  the  vector  diagram. 

The  armature  winding  is  closed  for  the  smallest  possible  number 
of  phases,  which  must  be  different  from  the  number  of  poles.  The 


DERI:     SINGLE-PHASE  MOTORS. 


303 


commutator  carries  the  exciter  brushes  at  right  angles  to  I  in  the 
axis  77.  The  brushes  are  connected  directly  or  by  means  of  a 
transformer  in  series  with  the  stator  winding.  The  working  cur- 
rents are  induced  by  Fl  in  the  short-circuited  armature  without 
brushes.  In  spite  of  the  short-circuiting  the  excitation  of  F2  in 
the  armature  winding  can  take  place  as  the  exciting  currents  flow 
partly  through  turns  of  the  armature  and  partly  through  short- 
circuiting  connections,  as  indicated  in  the  diagram  by  the  arrows 
and  as  represented  in  Fig.  24  more  clearly  in  the  case  of  a  four- 


Fig.  24 


pole  armature  having  a  six-phase  short.  The  field  flux  is  de- 
veloped of  variable  density  in  different  parts  of  the  pole  faces  but 
with  definite  polarity.  The  field  excited  by  a  part  of  the  ar- 
mature winding  and  held  fixed  by  the  brushes  attracts  the  short- 
circuit  currents  whereby  the  armature  is  set  in  motion.  With 
increasing  speed  there  appears  not  only  the  compensating  e.m.f. 
previously  referred  to  but  moreover  an  exciting  e.m.f.  which  has 
its  seat  in  the  closed  circuit  winding.  The  machine  constitutes  to 
a  certain  extent  an  externally  excited  and  consequently  externally 
controllable  induction  motor. 

The  e.m.f.  polygon  is  according  to  Fig.  23  ~dbcdea.  ~ae  ™  the 
e.m.f.  induced  by  rotation  in  the  self -excited  field,  fa  the  e.m.f. 
induced  by  rotation  in  the  externally  excited  field  Fz  in  phase  with 
Jt  and  'fo  that  induced  by  rotation  in  Ff  as  well  as  in  the  com- 
ponent of  F2  in  phase  therewith  and  ^  the  exciting  e.m.f.  con- 
sumed in  the  main  circuit.  Under  these  conditions  we  have  neg- 


S<J4  DERI:     SINGLE-PHASE  MOTORS. 

locted  the  angle  y  which  characterizes  the  phase  of  the  self-excita- 
tion, as  in  the  analogous  diagrams  of  the  other  commutator  motors. 

In  this  case  also  appears  the  compensating  effect  of  e.m.f.  de, 
to  improve  the  power  factor  as  well  as  the  power  output.  This 
e.m.f.  has,  moreover,  a  favorable  effect  on  the  operations  which  take 
place  in  the  short-circuit  of  the  induction  motor,  as  the  phase  di- 
rection of  the  working  current  be  is  brought  near  to  the  direction 
of  ce1  which  is  the  direction  of  the  cross-flux,  self  -excited  in  the 
.short-circuit  armature,  and  which  direction  departs  but  slightly 
from  db.  The  angle  /?  between  the  working  current  —  and  the 
total  flux  (be1  representing  the  resultant  of  the  e.m.f.  values, 
which  correspond  to  both  the  externally-excited  and  the  self-excited 
flux)  will  be  small.  Consequently  both  parts  of  the  combined 
motor,  even  at  speeds  much  below  synchronism,  are  found  to  be 
operating  under  favorable  conditions.  Cos  ^  can  be  made  equal 
to  unity  or  nearly  so,  just  as  in  the  case  of  the  compensated  motor. 
The  triangle  cfbc1  is  the  work  diagram  from  which  the  quantities 
T  ,  P  and  cos  <5  are  obtained. 

The  quantitative  relation  of  the  functions  are  as  follows: 

1.  In  the  total  machine  :    E  :  db  and  I:de; 

2.  In  the  externally-excited  machine:  E&:nl:l)c,  E^:n*I:de; 

3.  In  the  self-excited  machine  i.  e.,  in  the   induction  motor, 
E\  '  n*I  '  ae.    The  total  flux  Fz  is  composed  of  the  externally  ex- 

Tjl 

cited  component  (  :  J)  and  the  self  -excited  component  (  :—  :  n-I)  ; 

n 

and  at  ordinary  speeds  is  nearly  equal  to  the  sum  of  these  values. 
The  exciting  e.m.f.  necessary  to  expend  E~  :ce:bd  sin  (<?>  —  y^), 
which  is  measured  between  the  exciter  brushes  is  practically  small 
and  can  also  become  zero.  T:(l  +  n2)!2;  P:  n(i  -f-  ft2)/2  and 


This  kind  of  motor  is  far  superior  to  all  the  commutator  motors 
previously  described  as  regards  commutation.  Brushes  carrying 
main  working  currents  are  not  used;  therefore,  all  commutator 
difficulties  at  starting  and  at  low  speeds  disappear  entirely.  For 
this  reason  the  motor  becomes  nearly  independent  of  the  armature 
current.  Therefore,  from  this  standpoint  machines  can  be  built  in 
units  of  any  desired  size  quite  the  same  as  with  polyphase  motors. 
The  commutation  at  the  exciting  brushes  is,  as  previously  shown, 


DERI:     SINGLE-PHASE  MOTORS.  39o 

very  smooth,  particularly  in  this  case,  because  the  turns  in  closed 
circuit  under  the  brushes  are  really  parts  of  closed  circuits  and 
because  the  currents  which  flow  through  the  brushes  have  only  to 
furnish  a  small  part  of  the  excitation;  they  need,  therefore,  be 
comparatively  small  for  this  reason  and  especially  because  the 
brush  e.m.f.  ~^e  will  be  very  small  at  normal  speeds. 

The  commutator  for  this  reason  can  be  made  much  narrower, 
an  advantage  which  is  important  in  connection  with  the  fitting  into 
car  bodies;  of  equal  advantage  is  the  possibility  of  using  a  com- 
paratively small  number  of  brushes.  In  principle,  this  motor  is 
an  induction  motor  which  transmits  external  energy  by  means  of 
transformation  to  a  simple  rotor;  the  torque  and  speed  can  never- 
theless vary,  and  any  variation  can  be  produced  which  is  neces- 
sary for  the  control  of  vehicles  or  cars.  The  motor  can  be  started 
with  considerable  torque,  and  its  power  factor  can  be  made  nearly 
unity.  By  this  combination  we  have  an  externally  excited,  com- 
pensated induction  motor. 


ALTERNATING-CURRENT  MACHINES  WITH 
GRAMME  COMMUTATORS. 

BY  MARIUS  LATOUR,  Delegate  of  Societe  Internationale  des  Electriciens. 


If  we  refer  to  the  technical  literature  of  four  or  five  years  ago 
we  shall  notice  that  the  problems,  the  solution  of  which  was  sought 
by  engineers  applying  themselves  to  the  study  of  alternating-cur- 
rent machinery,  were : 

1).  The  development  of  alternators  in  which  all  difficulties  in 
parallel  running  should  be  done  away  with. 

2).  The  construction  of  generators  of  constant  voltage. 

3).  The  construction  of  motors  working  with  a  good  efficiency 
at  all  speeds,  and  starting  under  load  with  single-phase  current. 

4).  The  construction  of  non-synchronous  motors  working  with  a 
power  factor  equal  to  unity. 

It  was  about  that  time  that  I  began  to  take  an  interest  in  the  ap- 
plication of  the  Gramme  commutator  to  alternating-current  ma- 
chines. I  have  thus  been  led  to  a  new  system  of  electrical  machinery 
which  might  take  the  place,  either  as  generators  or  motors,  of  the 
machines  used  nowadays  and  solve,  from  the  technical  point  of 
view,  all  the  problems  set  forth. 

The  description  of  alternating-current  machines  comprising  a 
Gramme  commutator  is  comparatively  old.  Indeed,  it  is  to  be 
traced  back  to  Messrs.  Elihu  Thomson,  Wightman,  and  Wilson. 
However,  owing  partly  to  the  essential  phenomena  exhibited  in 
direct-current  armatures  traversed  by  alternating  currents  not  being 
very  well  known,  partly  to  the  little  interest  taken  by  electricians 
in  these  phenomena,  partly  to  the  bad  opinion  that  had  been  formed 
of  the  Gramme  commutator  used  in  connection  with  alternating- 
currents,  the  arrangements  proposed  by  those  inventors  were  left 
without  much  industrial  value. 

I  soon  realized  that  the  use  of  the  Gramme  commutator  with 
alternating  currents  was  full  of  capabilities  and  I  have  been  able 
to  realize  the  machines  concerning  which  I  shall  say  a  few  words. 

All  these  machines  have  a  uniform  appearance,  due  to  their 
comprising  a  stator  with  a  winding  distributed  in  slots,  and  a  rotor 

[39GJ 


LATOUR:     ALTERNATING-CURRENT  MACHINES.  :W7 

similar  to  a  direct-current  armature  with  a  commutator.  These 
machines  are: 

1).  The  panchronous  self-exciting  polyphase  generator. 

2).  The  panchronous  self-exciting  single-phase  generator. 

3).  The  polyphase  motor  at  variable  speed  with  a  power  factor 
equal  to  unity. 

4).  The  compensated  single-phase  motor. 

5).  The  repulsion  motor. 

6).  The  single-phase  series  motor  with  perfect  commutation. 

1.  The  Self -Exciting  Polyphase  Generator. 

This  generator  is  represented  in  its  two  most  interesting  shapes 
by  Figs.  1  and  2,  the  former  showing  the  shunt  connection,  and  the 
latter  the  compound  connection.  S  is  the  stator,  R  the  rotor  with 
commutator,  and  t  the  transformer  for  supplying  the  rotor.  Such 
generators  are  connected  to  a  network  like  direct-current  generators, 
without  any  synchronizing  operation.  The  compounded  alternator, 
when  well  regulated,  works  at  constant  voltage  whatever  may  be 
the  inductive  or  non-inductive  load  on  each  phase  separately. 

2.  The  Self -Exciting  Single-Phase  Generator. 

This  generator  is  represented  in  its  two  most  interesting  shapes 
by  Figs,  li  and  2X.  In  order  to  allow '  self-excitation  two  sets  of 
brushes  c  d  are  short-circuited  on  one  another.  In  reality,  for  the 
sake  of  commutation,  it  is  preferable  to  have  several  sets  of 
brushes  short-circuited  on  one  another,  as  represented  by  Fig.  3. 
The  self -exciting  single-phase  generator  has,  above  the  ordinary 
generator,  besides  the  two  advantages  regarding  the  easier  parallel 
running  and  the  perfect  compounding,  that  of  admitting  a  perfect 
rotary  field  without  any  harmonic  field  likely  to  weaken  the 
efficiency. 

3.  The  Polyphase  Motor  at  Variable  Speed  with  a  Power  Factor 

Equal  to  Unity. 

This  motor  corresponds  to  Fig.  1  (representing  the  shunt  con- 
nection of  the  panchronous  generator),  the  transformation  ratio  of 
the  transformer  t  being  supposed  to  be  arbitrary  and  variable.  The 
speed  of  the  motor  may  be  regulated  by  changing  the  transforma- 
tion ratio  of  the  transformer.  The  power  put  into  play  in  the  trans- 
former is  the  larger,  the  greater  the  slip  of  the  motor.  Such  a 
motor  may  work  with  a  power  factor  equal  to  unity  at  normal 
speed. 


398  LATOUR:     ALTEJtNATlXQ-UURlMNT  MACHINES. 


f!fl.4 


Fifl.6 


LATOUR:     ALTERNATING-CURRENT  MACHINES.  39tt 

4.  The  Compensated  Single-Phase  Series  Motor. 

This  type  of  motor  is  represented  under  its  two  forms  by  Figs. 
4  and  5.  Such  a  motor  works  at  every  speed  with  good  efficiency. 
The  power  factor  is  equal  to  unity  at  normal  speed,  and  magnetizing 
current  may  be  delivered  to  the  network,  if  desired. 

5.  The  Repulsion  Motor,  the  Stator  of  Which  Has  a  Distributed 

Winding. 


Flo.  «  Fig.  7 


This  type  of  motor,  represented  by  Fig.  6,  has  the  general  char- 
acteristics of  the  compensated  series  motor,  but  its  power  factor  is 
lower  and  the  leakage  has  in  this  motor  a  much  worse  influence. 

All  the  machines  of  which  I  have  just  spoken  have  a  common 
property  regarding  the  commutation,  viz.,  that  if  they  are  properly 
designed  they  work  with  a  perfect  commutation  in  the  vicinity  of 
synchronism,  owing  to  the  existence  or  the  formation  of  a  perfect 
rotary  field.  This  property,  which  I  have  demonstrated  for  each 
machine  successively,  although  at  first  questioned,  is  now  recognized. 

Let  us  consider  (Fig.  7)  a  direct-current  armature  which  is  re- 
volving under  the  action  of  a  rotary  field  in  a  stator  like  that  of 
an  induction  motor.  The  rotary  field  may  be  excited  partly  or 
completely,  either  from  the  stator  or  from  the  direct-current  arma- 
ture itself  if  this  is  traversed  by  alternating  current. 

Let  us  consider  a  section  s,  which  is  short-circuited  under  a 
brush  a.  The  revolving  field  may  be  considered  as  the  resultant  of 
two  alternating  fields,  the  first  one  <f>  sin  cot  in  a  direction  per- 
pendicular to  o  a;  the  second  one  <f>  cos  cot  in  the  direction  o  a 
itself. 


400  LATOUR:     ALTERNATING-CURRENT  MACHINES. 

Now  the  section  s  is  the  seat  of  two  e.m.f.s.  The  first  one  is  pro- 
duced in  a  static  way  by  the  variation  of  the  field,  <£  sin  cot,  and  is 
equal  to 

<h 

«j  =  —  GO  —  cos  GO  t . 
2 

The  second  one  is  produced  in  a  dynamic  way,  by  the  move- 
ment of  the  section  s  under  the  field  <£  cos  (&t,  and  is  equal  to 

d> 
e%  =  GOI  —  cos  GO  t, 

if  the  armature  is  revolving  at  the  angular  speed  GO^ 

These  two  e.m.fs.  are  opposite,  and  at  synchronism  (GOI  =  GO)  coun- 
terbalance one  another.  The  section  s  not  being  any  longer  the 
seat  of  any  resultant  e.m.f.,  the  commutation  under  the  brush  a 
will  be  perfect,  whatever  the  current  under  this  brush  may  be. 

This  consideration  leads  easily  to  the  conception  of  a  device  for 
avoiding  sparking  in  the  straight  single-phase  series  motor.  I 
wrote  a  paper  upon  this  device  a  few  years  ago,  and  Mr.  Maurice 
Milch,  working  independently  on  the  same  line,  has  reached  the 
same  result. 

6.  The  single-phase  series  motor  with  perfect  commutation. 

We  shall  consider  at  first  a  single-phase  series  motor,  the  field  of 
which  is  wound  like  a  direct-current  armature  (Fig.  8).  The  motor 


Ba.8 

being  operated  with  continuous  current,  in  order  to  obtain  the  best 
commutation  the  brushes  must  be  located  so  that  the  resultant  field 
of  the  motor  0  <j>  sin  cot  is  perpendicular  to  the  line  a  b.  When 
operated  with  single-phase  current,  if  the  induction  is  low  enough, 
the  power  factor  of  the  motor  will  be  pretty  high.  In  order  to 
reverse  the  direction  of  rotation  of  the  motor  without  shifting  the 


LATOUR:     ALTERNATING-CURRENT  MACHINES.  401 

brushes,  it  will  be  possible  to  change  the  position  of  the  terminals 
A  B  on  the  periphery  of  the  stator. 

Such  a  construction  represents  the  best  it  is  possible  to  obtain 
with  the  straight  single-phase  series  motor,  as  I  pointed  out  two 
years  ago  at  a  time  when  polar  projections  were  still  used. 

But  for  the  single-phase  series  motor  there  is  no  speed  for  which 
a  perfect  commutation  is  secured.  The  variation  of  the  field  of  the 
motor  induces  at  any  speed  an  e.m.f.  in  the  short-circuited  sec- 
tions, and  owing  to  this  very  important  reason,  I  think  the  series 
motor  is.  for  larger  capacities,  inferior  to  the  repulsion  motor  and 
to  the  compensated  type. 

Yet  we  can  improve  it  in  this  way :  An  auxiliary  field  '/''  cos  GO  t 
is  produced  above  the  short-circuited  sections,  which  field  lags  90 
deg.  behind  the  main  field,  <£  sin  (&t,  of  the  motor.  (See  Fig.  9.) 
Conforming  with  the  explanation  I  have  given  above,  it  is  easy  to 
see  that  the  new  e.m.f.  induced  in  the  short-circuited  sections  in  a 
dynamic  way  by  the  movement  of  these  sections  under  the  auxiliary 
field  Vf  cos  GO 1,  may  counterbalance  at  a  certain  speed  the  e.m.f. 
induced  in  a  static  way  by  the  variation  of  the  main  field  <£  sin  GO  t. 

The  auxiliary  field  may  be  excited  with  special  coils  c  c  shunt 
connected  to  the  motor,  these  coils  encompassing  only  a  few  slots. 

We  realize  now  that  four  types  of  motors  are  possible  for  single- 
phase  traction :  The  repulsion  type,  the  straight  series  motor,  the 
compensated  type,  and  the  type  with  an  auxiliary  field.  The  future 
will  decide  which  is  the  best. 

CHAIRMAN  DUNCAN:  The  next  paper  will  be  on  "The  Theory  and 
Operation  of  Repulsion  Motors,"  by  Mr.  Bragstad,  and  will  be  abstracted 
by  Mr.  Steinmetz. 

ELEC.  RYS. 26, 


SINGLE-PHASE  RAILWAY  MOTOES. 

BY  FRIEDR1CH  E1CHBERG. 


The  standard  direct-current  railway  has  probably  been  developed 
to  its  final  stage.  The  combination  of  alternating  current  for  the 
transmission  of  power,  rotary  converters  for  the  conversion  into 
direct-current,  and  direct-current  car  motors,  is  not,  however,  an 
economical  solution  except  in  rare  cases.  Recognizing  this  fact, 
Brown  &  Boveri  (Burgdorf-Thun)  and  Ganz  &  Company  (Valtelina 
line)  took  up  the  direct  application  of  polyphase  alternating  cur- 
rents. But  even  if  the  polyphase  system  has  achieved  practical 
success  in  special  cases,  it  has  not  been  proven  thereby  that  the 
polyphase  motor  furnishes  a  universal  solution  of  the  electric  rail- 
way problem.  It  is  not  necessary  here  to  repeat  all  the  objections 
that  European  and  American  engineers  have  brought  forward  in 
numerous  discussions  against  the  polyphase  motor.  The  multiple 
trolley  for  the  collection  of  current,  which  is  unavoidable  in  the 
polyphase  system,  leads  to  complications  in  the  overhead  work 
and  sets  narrow  limits  to  the  line  voltage  available.  For  short 
roads  (lines  between  neighboring  cities)  the  polyphase  system, 
moreover,  leads  to  excessive  cost  in  the  installation  of  the  conduct- 
ing system.  Add  to  this  that  the  polyphase  motor,  by  reason  of  its 
characteristic  speed-curve,  which  resembles  that  of  a  shunt- wound 
motor,  is  almost  or  quite  unfit  far  railway  purposes.  It  cannot  be 
disputed  that  it  is  possible  to  operate  on  schedule  time  upon  special 
lines  with  a  favorable  profile  but  this  proves  nothing  as  to  the 
general  applicability  of  the  polyphase  motor. 

For  two  years,  as  is  well  known,  efforts  have  been  made  to  apply 
the  single-phase  motor  to  railway  purposes.  B.  J.  Arnold,  with  his 
electro-pneumatic  system  and  the  Oerlikon  Company  with  the 
Ward-Leonard  system,  offered  only  incomplete  solutions  of  the 
problem  of  applying  single-phase  current  to  railways.  The  first 
announcement  of  the  direct  application  of  single-phase  motors 
came  from  Lamme,  of  Pittsburg,  and  was  followed  soon  after  by 
the  publication  of  Finzi  in  Milan.  The  former  used  a  frequency 
of  16,  and  the  latter  18  cycles  per  second.  Both  have  built  series 

[402] 


EICHBERG:     SINGLE-PHASE  RAILWAY  MOTORS. 


403 


motors  similar  to  the  direct-current  series  motor.  The  former  uses, 
for  the  compensation  of  the  armature  reaction,  short-circuited 
windings,  which  are  applied  in  the  field-magnet  coils  and  whose 
axis  coincides  with  that  of  the  brushes ;  the  latter  uses  slots  in  the 
poles  for  the  diminution  of  the  armature  reaction. 

Later  the  work  of  G.  Winter  (see  Elektrotechnische  Zeitschrift, 
1904,  No.  4),  of  Vienna,  became  known  to  the  writer.  This  fur- 
nished the  basis  of  the  system  worked  out  by  the  Union,  and 
especially  by  the  Allgemeine  Elektricitats-Gesellschaft.  This  sys- 
tem, which  forms  the  subject  of  this  paper,  has  been  put  into 
operation  on  the  Niederschoneweide-Spindlersfeld  line  under  the 
management  of  the  Koyal  Prussian  State  Kailway,  and  on  the 
Stubaital  line  near  Innsbruck,  which  was  opened  on  July  31,  1904. 
The  first  line  operates  with  6000  volts  and  25  cycles,  and  the  second 
with  2350  volts  and  42  cycles. 

In  perfecting  this  single-phase  system,  the  motor  of  course  played 
the  chief  part.  In  a  lesser  degree  the  controlling  apparatus  and 
those  devices  which  become  necessary  in  the  direct  application  of 
high  tension  to  the  car  were  also  of  importance. 

In  regard  to  the  motor  of  the  Winter-Eichberg  system,  it  unites 
the  properties  of  the  ordinary  alternating-current  series  motor  with 
those  of  the  repulsion  motor.  Its  characteristic  features  are  the 
following: 


FIG.  1. 


In  the  motor,  in  addition  to  its  own  magnetic  field  (F),  there  is 
developed  as  in  the  repulsion  motor,  a  cross-field,  0  which,  at 
synchronism,  is  about  as  strong  as  the  magnetic  field  F,  from  which 
it  differs  in  phase  by  90  deg.  This  means  that  when  the  motor  is 
near  synchronism  a  complete  rotary  field  is  established,  the  field 
being  less  developed  below  or  above  synchronous  speeds.  On 
account  of  the  cross-field  developed  in  the  motor,  the  short-cir- 
cuited e.m.f.  under  the  brushes  diminishes  with  increasing  speed, 
becomes  nearly  zero  at  synchronism  and  then  increases  again  with 
increasing  speed. 


404 


EICHBERG:     SINGLE-PHASE  RAILWAY  MOTORS. 


In  regard  to  armature  voltage,  these  motors  are  essentially 
similar  to  the  ordinary  series  motor.  In  both  the  tension  per  com- 
mutator segment  may  not  exceed  a  certain  value  and,  according  to 
the  size  of  the  motor,  the  armature  voltage  will  therefore  lie 
between  100  and  200  volts.  In  the  ordinary  series-motor,  in  which 
the  working  voltage  appears  in  the  armature,  the  working  voltage 
would  therefore  not  exceed  200  volts.  It  is  otherwise  with  our 
motor.  Since  the  armature  is  short-circuited  along  the  working 
axis  and  the  working  voltage  appears  only  in  the  stator  field  wind- 
ings, the  voltage  supplied  to  the  motor  may  be  as  great  as  desired. 
But  even  for  the  case  where  the  excitation  is  inserted  in  series  with 
the  stator  winding  (Fig.  2),  the  entire  working  voltage  (E)  is  in 
the  same  proportion  to  the  armature  voltage  (e)  at  rest  as  the 
entire  volt-ampere  input  is  to  the  volt-amperes  for  magnetization 
at  rest. 


(150  Volts) 

Ed- 

(450Volt«) 

Volts 

FIGS.  2  AND  a 

Let  us  suppose  that  the  magnetizing  current  is  one-third  of  the 
armature  current,  which  is  a  good  practical  mean;  then  the  work- 
ing voltage  in  the  motor  of  our  system,  even  with  the  direct  intro- 
duction of  the  excitation,  is  three  times  as  high  as  in  the  ordinary 
series  motor.  Through  the  insertion  of  a  small  transformer 
(Fig.  3)  one  can  increase  at  will  the  proportion  of  the  working 
voltage  to  the  armature  voltage  without  great  expense  (Figs.  2 
and  3). 

The  excitation  by  means  of  the  armature  in  combination  with 
the  cross-field  yields  an  e.m.f.  which  is  90  deg.  ahead  of  the  w.ork- 
mg  e.m.f.  and  directly  opposite  to  the  e.m.f.  of  self-induction. 
This  wattless  counter  e.m.f.  gives  the  motor  the  well-known  rapidly 
rising  cos<£  curve.  (See  EUJctrotechnische  Zeitschrift,  1904, 
No.  4.)  Our  first  100-hp  motor  had,  with  a  3-mm  air-space  on 
each  side,  a  power  factor  of  0.9  even  at  70  per  cent  of  synchronism. 
Even  more  important  is  the  fact  that  this  good  power  factor  is 
obtained  with  a  number  of  ampere-turns  per  cm  almost  twice  as 


ElCHBtiltU:     SINGLE-PHASE  RAILWAY  MOTORS. 


405 


great  as  in  the  ordinary  alternating-current  motors.  From  this 
results  the  possibility  of  building  a  very  powerful  motor  for  a 
given  armature  diameter  and  external  dimensions. 

Another  characteristic  property  of  our  system  is  that  the  field 
can  be  controlled  independently  of  the  voltage  in  the  working 
windings.  In  every  alternating- cur  rent  commutator  motor  there 
are  magnetic  losses  in  the  coils  short-circuited  by  the  brushes. 
Through  the  possibility  of  adjusting  this  field  in  proportion  to  the 
stator  current,  one  can  keep  these  losses  under  the  brushes  within 
Fuch  limits  as  will  permit  the  commutator  and  the  brush-holders 
easily  to  conduct  away  the  resulting  heat.  By  varying  the  field 
one  can,  for  a  given  working  voltage,  give  the  motor  a  variable 
characteristic.  The  separate  characteristic  curves  will  then  be 
somewhat  related  as  the  curves  of  a  3-,  4-,  5-  and  6-winding 
motor.  Control  independent  of  this  naturally  is  possible  and 
also  control  of  the  load  voltage.  The  accompanying  diagrams 
give  examples  of  the  control  as  carried  out  in  practical  cases.  In 
Fig.  4  the  primary  voltage  is  not  regulated  and  only  the  secondary 
winding  of  the  exciting  transformer  is  altered. 


rAAAA/V WW\A— j 


FIGS.  4  AND  5. 

The  absence  of  any  primary  regulation  in  the  high-tension  cir- 
cuit offers  the  special  advantage  that  only  low-tension  circuits  will 
have  to  be  opened  or  closed  when  the  car  is  to  start,  reverse  or 
alter  its  speed.  A  still  more  complete  solution  is  shown  in  Fig.  o, 
the  stator  circuit  as  well  as  the  exciter  circuit  being  regulated. 
This  method  of  connection  is  less  advantageously  applied  to  high- 
tension  motors,  because  the  high-tension  circuits  generally  can  not 
be  readily  altered  in  operation. 

The  third  diagram  (Figs.  6a  and  6b)  shows  a  method  of  con- 
trol which,  although  not  quite  so  complete  as  that  of  Fig.  5,  is 
yet  of  value  for  small  low-tension  cars,  and  which  will  shortly 
bo  put  into  operation  on  a  short  Belgian  road.  The  scheme  of 


406 


EICHBERG:     SINGLE-PHASE  RAILWAY  MOTORS. 


Fig.  5,  with  the  modification  represented  in  Fig.  7,  was  installed 
on  the  Stubaital  line  near  Innsbruck,  now  in  operation,  which  is 
at  times  operated  at  2350  volts  and  at  other  times  at  400  volts. 
The  direct  insertion  of  the  excitation  in  the  stator  circuit  (Fig.  2) 
in  which  the  control  is  effected  by  ohmic  or  inductive  resistances 


Volts 


120 
VolW 


Volts 

FIGS.  6A  AND  GB. 


120 
VolM 


with  the  eventual  application  of  series-parallel  regulation,  is  pos- 
sible for  small  cars,  and  hence  chiefly  applicable  to  short  railway 
lines.  In  the  latter  case  the  motors  can  be  built  simply  for  550 
volts.  Motors  for  550  volts  connected  in  this  manner  are  already 
in  operation,  and  will  also  run  on  direct-current  lines.  (Figs.  7a 
and  7b.) 


/WWWNAAAAj 

V  2850  Volts   «• 


FIGS.  TA  AND  7s. 


The  possibility  of  running  an  alternating-current  motor  with 
direct  current  is  of  great  importance  in  practical  application. 
Ordinary  series  commutator  motors,  which  are  built  on  the  com- 
pensated system  of  Deri,  can  of  course  be  run  both  on  direct- 
current  and  alternating-current  circuits.  The  voltage  for  the 
direct-current  motor  is  l1/^  to  2  times  higher  than  the  armature 


EICHBERG:     SINGLE-PHASE  RAILWAY  MOTORS.  407 

voltage  with  alternating  current.  Since,  as  we  have  shown  above, 
the  alternating-current  voltage,  which  in  our  motor  system  can 
be  directly  applied,  may  be  three  times  greater  than  the  armature 
voltage,  the  ratio  of  direct-current  to  alternating-current  voltage 
will  be,  not  as  in  the  series  motor  3:1^  or  3  :2,  but  3:3  to  1% 
or  2;  that  is,  the  direct-current  voltage  will  be  about  half  that 
of  the  alternating-current  voltage.  This  allows,  for  example,  the 
running  with  direct  currents  with  motors  connected  in  series,  and 
with  alternating  current  with  the  motors  connected  in  parallel, 
but  in  the  former  case  at  less  speed.  This  corresponds  to  the 
case  in  common  practice  where  cars  which  travel  over  interurban 
stretches  at  high  speed  transfer  to  the  direct-current  systems  of 
cities,  where  lower  speed  is  demanded.  There  are  various  ways 
of  running,  with  a  motor  connected  according  to  Fig.  1,  on  direct- 
current  circuits.  The  method  which  has  proved  itself  most  prac- 
tical is  represented  in  Fig.  8.  In  the  direction  of  the  diameter 
of  the  exciter  axis  a  winding  is  applied  which  counteracts  and 
opposes  the  armature  ampere-turns.  The  stator  field  windings 
then  produce  a  magnetic  field  with  direct  current,  and  the  exciting 
windings  on  the  armature  represent  with  direct  current  the  work- 
ing ampere  windings.  The  field  saturation  in  direct  current 
working  is  then  somewhat  greater  than  with  alternating  current, 
while  the  density  in  the  armature  is  somewhat  less.  These  prop- 
erties are  extraordinarily  favorable  for  practical  operation.  The 
auxiliary  winding  (h)  is  inserted  only  when  operating  with  direct 
current.  In  order  to  make  better  use  of  the  armature,  the  field 
windings  of  two  motors  can  be  connected  in  parallel  in  the  direct- 
current  circuit,  while  in  order  to  be  able  to  operate  at  500-550 
volts  with  direct  currents,  the  armatures  can  be  connected  in  series. 
These  conditions  are  represented  in  Fig.  9.  In  the  alternating- 
current  system,  one  can  operate  according  to  the  method  of  either 
Fig.  3  or  Fig.  G.  If  operated  according  to  plan  3,  then  with  alter- 
nating currents  the  connections  2,  4,  5  are  closed  and  1  and  3  are 
open.  With  direct  current,  1  and  3  are  closed,  and  2,  4  and  5 
are  open. 

The  motor  system  which  I  have  above  briefly  described  will  not 
be  the  only  one  in  the  field.  I  can  not,  however,  undertake  to 
pass  an  unbiased  opinion  upon  the  different  systems  possible.  I 
can  only  briefly  mention  the  reasons  why,  in  my  opinion,  the 
alternating-current  commutator  motor,  which  has  been  long  known 
in  two  general  types,  namely,  the  ordinary  series  motor  and  the 


408 


EIGHBERG:     SINGLE-PHASE  RAILWAY  MOTORS. 


repulsion  motor,  is  not  to  be  considered  of  equal  value  to  the 
system  above  described.  The  ordinary  series  motor  possesses,  even 
if  it  is  compensated,  no  cross-field;  and  it  has  no  rotary  field. 
The  short-circuit  losses  under  the  brushes  do  not  decrease  with 
increasing  speed,  and  the  power-factor  increases  much  slower  with 
the  speed.  The  maximum  working  voltage  for  which  it  can  be 
built  is  200  volts.  When  a  short  circuit  takes  place  in  the  field 
winding  of  the  series  motor,  the  motor  becomes  inoperative. 
Multipolar  machines  with  series  windings  on  the  armature,  if  pro- 
vided with  the  device  shown  in  Fig.  1,  can  have  an  entire  field 
coil  short-circuited  without  the  motor  becoming  inoperative.  The 
separate  field  coils  behave  like  transformers  inserted  in  series. 
Any  one  of  these  can  always  be  short-circuited;  the  others  then 
receive  correspondingly  more  voltage. 


FIGS.  8  AND  9. 

The  repulsion  motor  when  contrasted  with  the  arrangement  of 
Fig.  1  has  the  disadvantage  that  its  reversal  is  possible  only  by 
the  application  of  a  second  field-winding,  or  of  several  sets  of 
brushes,  or  of  reversible  brushes.  Its  power-factor  is  poorer,  and 
for  its  control  there  remains  only  either  the  method  of  primary 
voltage  control,  the  opening  of  short  circuits,  or  finally  of  brush 
reversal. 

The  disadvantage  of  the  type  represented  in  Fig.  1,  as  com- 
pared with  the  series  and  repulsion  motor,  consists  in  the  employ- 
ment of  two  exciter  brushes,  which  doubles  the  number  of  brushes 
in  multipolar  systems.  These  exciter  brushes  give  rise  to  no  diffi- 
culties with  respect  to  short-circuit  losses;  as  I  have  shown 
(Elektrische  Bdknen,  Vol.  2,  1904),  these  short-circuit  losses  do 
not  occur  with  exciter  brushes.  They  carry  moreover  only  one- 


EWE  BERG:     SINGLE-PHASE  RAILWAY  MOTORS.  409 

third  to  one-fourth  of  the  entire  short-circuit  current.  On  the 
other  hand,  the  motor  of  Fig.  1,  as  compared  with  the  compensated 
series  motor  and  the  repulsion  motor  with  the  double  field-winding, 
offers  the  constructional  advantage  of  only  one  field  phase,  which 
guarantees  good  economy  and  great  simplicity.  In  high-tension 
motors,  the  increased  certainty  of  operation  in  consequence  of  the 
absence  of  cross  windings  must  be  considered.  Motors  for  either 
direct-current  or  alternating-current  working  provided  with  the 
auxiliary  winding  (h),  which  plays  the  part  of  the  compensation 
winding  of  the  compensated  series  motor,  can  therefore  only  be 
operated  advantageously  with  low-tension  alternating  currents. 

The  results  of  more  than  a  year's  operation  on  the  6000-volt 
Niederschoneweide-Spindlersfeld  line,  on  which  during  a  great 
part  of  the  day  four  100-hp  motors  haul  a  160-  to  170-ton  train, 
and  on  which  daily  two  motors  handle  a  100-ton  train,  prove  that 
the  alternating-current  motor  is  adapted  to  the  heaviest  traffic. 
Moreover,  the  direct  application  of  6000  volts  to  the  car  has  been 
demonstrated  to  be  entirely  safe. 

The  Stubaital  line,  which  has  been  running  since  July  31,  1904, 
at  42  cycles  and  2350  volts,  has  introduced  an  advanced  practice 
for  small  roads,  an  advance  which  exceeds  the  boldest  expectations 
of  the  year  1902.  At  that  time  it  seemed  as  though  only  very  low 
frequencies  could  be  used.  In  the  case  of  many  roads  running  in 
connection  with  existing  power  stations  operating  with  40-50 
cycles,  the  possibility  of  using  these  frequencies  limits  the  availa- 
bility of  alternating-current  traction.  Moreover,  the  possibility 
of  operating  also  with  direct  current  makes  the  alternating-current 
commutator  motor  in  a  certain  sense  a  universal  motor,  and  places 
it,  as  regards  its  main  features,  far  above  the  direct-current  com- 
mutator motor,  which  really  represents  only  a  special  case  of  the 
alternating-current  commutator  motor. 


THEORY  AND  OPERATION  OF  THE  REPULSION 

MOTOR. 

BY  0.  S.  BRAGSTAD. 


Commutator  motors  for  alternating  current  have  become  of 
great  interest  within  recent  years.  The  main  reason  for  this  is 
the  demand  for  a  motor  for  single-phase  alternating  current  for 
the  operation  of  electric  railways  ;  but  such  motors  will  also  find  a 
broad  field  for  other  purposes  where  speed  regulation  is  required. 

Of  special  interest  in  the  older  forms  of  alternating  commutator 
motors  is  the  repulsion  motor,  important  in  itself  as  also  in  that  it 
marks  a  transition  to  the  different  forms  of  compensated  motors. 

In  the  following  I  will  develop  a  general  theory  of  the  repulsion 
motor,  and  that  under  the  usual  assumptions  that  the  magnetic 
resistance  is  constant  for  all  magnetic  circuits,  and  that  the  iron 
losses  are  proportional  to  the  square  of  the  induction.  We  will  not 
consider  the  processes  under  the  commutator  brushes  and  in  the 
armature  coils  short-circuited  by  the  brushes. 

PRINCIPAL  EQUATION. 

Fig.  1  shows  the  diagram  of  the  motor.    Wg    is  the  stator  and  WT 
the  rotor  winding.    The  angle  of  displacement  relative  to  the  shaft, 
Y  —  Y  ,  of  the  stator  winding  is  «.     We  further  take  : 
Is    the  stator  current  according  to  strength  and  phase, 
1T    the  rotor  current  according  to  strength  and  phase, 
EJ  the  induced  e.m.f.  according  to  strength  and  phase,  in  the 
stator  winding,  we  get  the  following  relation:1 

l)E's  =  -  Za  (/s  +  /r  COS  «)  =/m  Z&  . 

In  this  we  assume  the  effective  number  of  windings  of  the  stator 
winding  and  of  the  rotor  winding  to  be  alike.  Z&=  r&  —jxA  can  be 
df3signated  as  the  exciting  impedance  of  the  motor  and  is  given 
through  the  magnetic  resistance  of  the  main  power  current  of  the 


same,  whereby  ra  is  so  determined,  that  E'l  ~2~T  —  2~ 

*&   ~T~  •£» 


1.  The  period  below  the  letter  indicates  that  the  value  is  a  vector  of 
determinable  phase. 

[410| 


BRAGSTAD:    REPULSION    MOTOR.  411 

equal  to  the  iron  effect.    7m  is  the  resulting  current  in  the    Y  axis, 

or  the  magnetizing  current  in  this  axis.    In  the  rotor  winding  there 

i*j  induced  between  the  brushes  through  the  same  power  current: 

1) .  Statically  E'rj  =  E'%  cos  a  =  —  Za  (/•  +  /r  cos  a)  » 

—  Za  7m  COS  a. 

2).  Dynamically  through  the  rotation: 

.u  r  u  .  u  .    .    T-    • 

fj'    d  as  —  1  —  Es  81D  a  =  —  9  Za  (A  +  /r  COS  a)  SID  a  =  —  7  Z»  ^m  SID    a 

"  c    •  c "  c 

where  w  is  the  number  of  periods  of  the  rotor  rotation. 
c,  number  of  periods  of  the  current, 
;=   4/_  i. 
The  prefixed  sign  depends  on  the  direction  of  rotation  chosen. 


The  rotor  current  generates  a  power  current  in  the  X  —  axis, 
perpendicularly  to  the  axis  of  the  stator  winding.  The  e.m.f.  in- 
duced by  this  power  current  is  between  the  brushes  : 

1).  Static 

3)  ^/rx  =  -Za^r8m2a. 

2).  Dynamic,  through  the  rotation 


4)    E'rxA  =j  ~  E'rx  COS  a  —  -      j  Za  fr  SID  a  COS  O. 

The  prefixed  sign  must  be  the  reverse  in  equation  4  to  what  it  is 
in  equation  2. 
From  2  and  4  follows 

E'ryd  +  #'rxd  =J  ^  Za  /.   sin  O. 


412 


BRAGSTAD:     REPULSION    MOTOR. 


The  field  generated  by  the  rotor  current  Ir  thus  produces  no 
dynamic  e.m.f.,  which  also  follows  from  the  fact  that  the  same 
runs  along  the  brushes. 

The  entire  e.m.f.  induced  in  the  rotor  must  be  equal  to  the  rotor 
current,  lt  times  the  impedance  of  the  rotor  winding,  which  we 
will  designate  by  Zr.  We,  therefore,  have 

—  Za  's  COS  a  —  Z&  IT  COS2  a  —  £a  7"r  Sin2  a  -f  -j  Z*  IB  Sin  a  =  IrZr 

•  •  *  C  ' 

IT  (Za  +  Zr)  ——  fs  (cos  a  —  U~j  sin  a)  Za 
l]  fr  =  —  £  (cos  a  —  U-j  sin  aj  J8 

II)  E'6  =  -  (Za  -  1^  (cos2  a  —  -j  si 
/  .  \  c 


and 


sn  a  cos  a 


)  )  7. 

/  /   • 


where 

Zt=  Z&~{-  Zr> 

Let  us  designate  by  ZB  the  impedance  of  the  stator  winding; 


FIG.  2. 

then  the  corresponding  e.m.f.  is  equal  to — IgZs,  and  the  entire 
e.m.f.  in  the  stator  winding 

77T/  ET/  T     /7 

.o    •^Ja  s  —  ^s  //a  • 

Or  if  we  introduce  instead  of  the  e.m.f.  the  terminal  pressure, 
E  =  —  E')  we  have 

III)  E=  Is  (zs  +  Z&  —  |^  (cos2  «  -  %j  sin  «  cos  «))  . 

j^t 

From  this  we  get  for  a  given  constant  stator  current  /g  =  Is,  the 

pressure  diagram  shown  in  Fig.  2.     We  assume  the  direction  of 


BltAGSTAD:     REPULSION    MOTOR.  413 

rotation  of  the  vectors  to  be  to  the  right  and  carry  0  A  =  7g  onto 
the  vertical  axis.    If  we  further  have 


we  have 


-T9  and  BF  =  In 

A  A      * 

whereby  we  make  the  triangle  BFD  similar  to  the  triangle  BCE. 
We  determine  a  point  G  on  the  straight  line  FD,  so  that 


cos2   a,   draw  a  perpendicular  line  to  DF  at  (r  and  make  GU  = 

—  DF  sin  «  cos  «.  0  £7  then  represents  the  terminal  pressure  E  of 
c 

the  motor  for  the  respective  number  of  revolutions  u,  and  <p  is  the 
augle  of  lag  of  the  current.  At  standstill  of  the  motor  (u  =  o) 
point  U  coincides  with  G.  OG  is.  therefore,  the  terminal  pressure 
at  standstill.  With  increasing  positive  speed  the  terminal  point 
of  the  pressure  vector  OU  moves  upwardly  on  the  perpendicular. 
When  reversing  the  direction  of  rotation,  the  point  moves  down- 
wardly. The  machine  is  then  converted  into  a  generator. 

Through  equation  1  we  can  also  easily  find  the  rotor  current  7r  in 
the  diagram.  We  make  similar  the  triangles  OKA,  BCEt  and  BFD, 

AL 


and  set  up  at  point  L  a  vertical  line  LM  on  AK.    On  this  vertical 

line  we  mark  off  the  distance  LM  =  —    sin  «  AK,  then  we  have 

c 

for  the  respective  number  of  revolutions  u  AM  =  Ir  according  to 
quantity  and  phase.  The  terminal  point  of  the  vector  7r  moves 
with  a  variable  number  of  revolutions  on  a  straight  line  similarly 
to  the  vector  of  the  terminal  pressure.  If  we  make  AN  =  AM 
cos  «,  then  ON  '==,  jT  -f-  Ir  cos  «  =*  1^  (see  equation  1).  ON 
thus  represents  the  magnetizing  current.  With  a  variable  number 
of  revolutions  u,  point  N  moves  on  a  straight  line  NR  perpendicu- 
lar to  AK,  and  AR  =  AK  cos2  «.  It  is  seen  that  the  two  figures, 
OKRAN  and  BFGDU,  are  alike,  and  that  every  length  of  the 
second  has  developed  from  the  corresponding  length  of  the  first 
through  multiplication  by  0a  and  rotation  about  an  angle  equal  to 


414  BRAGSTAD:     REPULSION    MOTOR. 

arc  by  JE*.       Furthermore,  the  latter  figure  is  displaced  from  the 

r& 
initial  point  by  the  length  OB  =  ISZ8. 

Whilst  in  a  series  motor  with  constant  current  the  field  remains 
constant  and  the  e.m.f.  proportional  to  the  speed  is  dynamically 
developed  through  the  rotation  speed  of  the  induced  (armature) 
winding,  we  have  in  the  repulsion  motor  in  the  primary  winding, 
because  the  same  is  stationary,  only  a  statically  induced  e.m.f.  and 
the  change  of  the  same  with  the  speed  is  caused  by  a  corresponding 
change  of  the  field  in  the  axis  of  the  stator  winding.  This  change 
is  proportional  to  GU  in  the  diagram.  The  field  in  the  X  axis  i& 
proportional  to  7r  sin  a  and  likewise  increases  with  the  speed. 

MOMENT  OF  ROTATION,  OUTPUT,  AND  DEGREE  OF  EFFICIENCY. 

The  moment  of  rotation  which  acts  on  the  armature  is  obtained 
if  we  multiply  the  pressure,  produced  in  an  axis  of  the  armature 
winding  through  the  static  induction,  by  the  current  component 
displaced  thereto  by  90  deg.  in  the  second  perpendicular  axis.  The 
moment  of  rotation  is  then  obtained,  expressed  in  the  number  of 
watts  which  the  same  would  put  out  at  synchronism.  If  we  arbi- 
trarily assume  the  two  vertical  axes,  we  must  as  a  general  rule 
carry  out  two  multiplications  and  add  up  the  two  products. 

Here  we  must  consider  every  axis  once  as  current  axis  and  then 
as  pressure  axis.  If,  however,  we  so  chose  the  two  perpendicular 
axes  that  either  the  current  or  the  pressure  becomes  zero  in  one 
axis,  then  one  of  the  two,  products  disappears  and  we  need  make 
but  one  multiplication. 

In  the  present  case  we  put  the  one  axis  through  the  armature 
brushes  and  the  second  one  perpendicularly  thereto.  The  current 
i.n  the  direction  of  the  second  axis  is  then  zero,  and  we  only  need 
to  form  the  product  from  the  pressure  in  the  perpendicular  direc- 
tion to  the  armature  brushes  and  the  rotor  current  displaced  rela- 
tive thereto  by  90  deg. 

This  pressure  is 

Za/8  sin  a  =  A/g  Zt  sin  a. 
A   • 

and  the  rotor  current  is 

Ir  =  —  ^r  (cos  a J  sin  a)  /• 

Zit  c 

The  product  is  obtained  as  the  imaginary  part  of  the  product, 
after  having  changed  the  prefixed  sign  of  the  imaginary  current 


BRAGSTAD:     REPULSION    MOTOR.  415 

• 

g 

component.      We   so   chose   the  phase   of  78  ,  that  —  /8    becomes 

Zt   * 

actually  equal  to  JL  j^  where 


and 


The  moment  of  rotation  is  then 
J)  =  l]a  -f?:  J    ,  imaginary  part  of  (  —  cos  a——,;  sin  a)   (rt  —jx  J  sin  a 

I  V)  D  =  (lB  ^)  2  («t  8in  a.  cos  a    -  !f  rt  sin2  a\ 

We  can  then  determine  by  differentiation  the  brush  angle  a,  for 
which  the  moment  of  rotation  for  a  given  current  78  becomes  a 
maximum.  We  get 

5)  tan  2  a=  —    — 


At  the  start  u  =  0,  thus  ta>*  2  a  =  oo  «  =  45  deg.  With  an  in- 
creasing speed  a  is  somewhat  decreased.  At  synchronism  (u  =  c) 
we  get 


5a)  tan 

With  «  =  45  deg.  the  moment  of  starting  is 


and  the  moment  at  synchronism 


The  energy  transformed  into  mechanical  work  is  found  simply 
by  multiplying  the  moment  of  rotation  by   —  .    It  is  thus 

V)  Hm=  "ft  =  (l*  y-)2  ("  ajt  sin  a  cos  a-  (")  '  rt  sin2  a)  . 

According  to  equation  III  we  have  for  the  terminal  pressure,  if 
we  put  1%  =1* 


III 


^=/8  (Zg  +  Za  —  Z  (cos2  a—  ^;  sin  a  c  OB  a)  ) 


—        sn  a  cos 


=  7.  (rg  —  r  oos"  a  +  —  x  sin  a  cos  a  —  ^  f  j;g  —  #  cos*  a  — 

' 


u 

—r  flu  a  cos  a 

c 


410  BRAGSTAD:     REPULSION    MOTOR. 

—  -C  (rk  H  —  «  sin  a  cos  a  —  J  lxk  --  r  sin  a  COP  a\  \  . 

The  following  abbreviations  have  here  been  introduced: 

Z&2  I  \ 

-*—-=Zs=sr  —  jx    (constant  section  FD  in  Fig.  21 

Z*  +  Z&  =  rs  +  r&-j  (ajg  -f  a;a) 
*=Zg  =  rg  —  jxg    (constant  section  OZ>in  Fig.  2) 
Zg  —  Z  cos2  a  =  rg  —  r  cos2  a  —  j  (xg  —  x  cos2  a) 
=  Zk=ryi  —j  Xk    (section  OG  in  Fief.  2) 

^k  is  the  impedance  of  the  motor  at  standstill  (short-circuit  im- 
pedance), and  is  dependent  on  angle  a. 
For  a  =  o  we  have 

Zk=Z3  +  ^^-    (section  OF  in  Fig.  2.) 

Witji  an  increasing  angle  of  displacement  of  the  brushes,  the  ter- 
minal point  of  the  vector  Zk  moves  on  the  straight  line  FD  from 
F  to  D.  For  a  =  90  deg.  we  have 

Z^=Z8-\-Z&  =  Zs    (section  OD  in  Fig.  2). 
From  equation  V  we  can  determine  the  number  of  revolutions 
we    for  which  the  output  of  the  motor  becomes  naught.     The 
same  is 


c         rt  sin  a 
For  this  no-load  point  we  get  the  phase  displacement   ?e    by 

putting  the  above  value  of  -1   into  equation  Ilia.    We  get 


Xt 

—  —  T 


tan 


Ze  =  re  —  jfy  can  be  designated  as  the  no-load  impedance  of  the 
motor.    We  can  also  put 


11)     =ZK  — 

From  this  we  immediately  get  the  following  construction  of 


BRAGSTAD:     REPULSION    MOTOR. 


417 


(Fig.  3).  We  make  OB  =  Ze  and  BE  =  Zt  =rt—jxt equal  to  the 
geometrical  sum  of  BD  and  DE,  whereby  BD  =  Z&  and  DE  =Zr . 

Z  2 

Thereupon  we  draw  the  line  DP  =  Z  =  -~  and  set  up  at  F,  a  ver- 

A 

tical  FS.    The  angle  FDS  becomes  equal  to  arcta/*  —  and  -y-,= 

y*j  W  ».N 

cos2  a.  OT  is  then  the  vector  of  the  no-load  impedance.  The  termi- 
nal point  of  the  vector  of  the  short-circuit  impedance  is  G  and  this, 
point  is  the  projection  of  point  T  onto  section  Z  =DF.  For  a  = 


FIG.  3. 

90  cleg.,  cos  a  =  o,  the  no-load  point  8  coincides  with  the  short- 
circuit  point  G  in  point  D.  With  the  decrease  of  angle  a,  the  no- 
load  point  moves  toward  S  and  the  short-circuit  point  toward  F. 

From  equation  V  we  find  the  maximum  output  of  the  motor  for  a 
constant  current,  if 


12) 


u 
Xt  sin  a  cos  a  —  2  —  rt  sirr  a  =  o 

1        cos  a 

sin  a  " 


c        2  rt 

The  maximum  output  with  constant  current,  therefore,  occurs 
when  the  motor  has  half  of  the  no-load  speed  (see  equation  9). 
This  maximum  output  would  be 

ELEC.  RYS. 27. 


418  BRAQSTAD:     REPULSION    MOTOR. 

If  we  introduce  the  number  of  revolutions  for  the  maximum  out- 
put into  equation  IIIa),  we  have 

I       *     Xt  2  •/  I**  9      \ 

+  —  —  X  cos2  a  — j  (xk  —  5 r  COS2  a) 

2  rt  \          2  r^  j 

Or  in  consideration  of  equation  10: 

14)  E=  78  ft  (rk  +  re )  -j  (i  (*k  +  x.  ) )). 

This  result  also  follows  directly  from  the  fact  that  the  point  for 
maximum  output  lies  in  the  middle  between  the  short-circuit  point 
and  the  no-load  point. 

The  general  expression  for  the  electric  power  supplied  to  the 
motor  is 

15)  W9  =  Jg 2   (rg  —  r  cos2  a  -j — x  sin  a  cos  a  j 

T   9     /  ,      U  ' 

— 1%  2  (rk  -{-  -x  sin  a  cos  a 
\          c  j 

The  degree  of  efficiency  is  thus 

jj7          2»2  [—Xt  sin  a  cos  a 5  rt  sin2  a  ) 

16)  w^IlB^ ^£ £ 9 

W«              2  /       ,   u  \ 

•b      I  rk  H *  8m  a  COS  a  1 


c  / 

By  differentiation  we  find  from  this  the  number  of  revolutions 
foi  the  maximum  degree  of  efficiency 


,        *t 
2 


_  __ 

C  x  sin  a  cos  a  x2  sin2  a  cos2  a       rt  X  sill2  a 

The  negative  prefix  of  the  root  would  apply  to  the  operation  as 
generator.  We  here  take  the  positive.  The  expression  can  be  easily 
reduced  to  the  following: 

17)  U_      ^^e  —  y*k 

G         x  sin  a  cos  a 

This  expression  for  the  most  favorable  number  of  revolutions  in- 
troduced into  equation  16  gives  for  the  maximum  degree  of  ef- 
ficiency the  following  value  : 


,  Qv  2a  2   (2  rk  rt  +  xtx  cos2  a)  Vrk  re—  2  rt  rk  r€ 

1OJ       Viaax  —  —  I  -  ~        /  — 

zt  2  x>  cos2  a  Vrk  re 

The  values  for  the  most  favorable  number  of  revolutions  (17), 
and  for  the  corresponding  degree  of  efficiency  (18)  are,  as  is  seen. 
independent  of  the  chosen  current  strength  and  of  the  terminal 
pressure.  If  the  current  strength  is  assumed,  we  find  the  terminal 
pressure  through  the  introduction  of  the  respective  number  of 


BRAGSTAD:     REPULSION    MOTOR.  419 

revolutions  into  equation  IIIft.  We  likewise  obtain  the  output  of 
the  motor  by  introducing  the  number  of  revolutions  into  equa- 
tion V. 

OUTPUT  DIAGRAM  WITH  CONSTANT  TERMINAL  PRESSURE. 

The  mode  of  operation  of  the  motor,  assuming  a  constant  current, 
can  be  quite  plainly  seen  in  the  pressure  diagram  of  Fig.  2.  This 
diagram  is  useless,  however,  when  it  is  a  question  of  examining  the 
action  of  the  motor  with  a  constant  terminal  pressure.  We  will 
now  also  develop  a  diagram  for  this  case. 

In  equation  II  I  we  assume  the  terminal  pressure  to  be  real,  in 
that  we  put  E=  E  but  we  allow  the  current  vector  to  take  any 
arbitrary  phase.  Equation  IIIathen  reads 

IIIby  E=  78    ^k  -|-  _  x  sin  a  co*  a  —  j  \rr  --  r  -in  a  cos  «  j  j 

For  the  current  Zg  we  will  introduce  the  two  components,  the 
real  one  ^  parallel  to  e  and  the  imaginary  one  C,  perpendicular 
to  e.  We  thus  put 

h  =  *>  +<?  * 

Because  the  imaginary  must  disappear  on  the  right  side  of 
equation  II  Jb),  we  have 

19)       £  ^rk  -f  —  x  sin  a  cos  a  j  —  T?   ^  xr  —  —  r  sin  a  cos  a) 
and  from  this 

19a)  -£x  -I-7??*    sin  a  cos  a  =  77  xk  -  c  rk 


From  this  we  can  deduce  the  following  two  equations: 


u  f"x\i  —  c  >?  ^t 

—  x  bin  a  cos  a=      „        -  '  —  -  x 

c  c  x  -\-  rj  r 


T 

If  we  introduce  these  two  values  into  equation  19,  we  get: 

«  V£  a;  +  TI  r)  =  (?  2+ry2  )  (r  rk  +  a;  «k  ) 
or 

vi)  /82=  *  2+  ^  _  .  l_^-hA_r_ 

r  rk  +  a;  xk 

If  we  consider    ?  as  abscissa  and    ^  as  ordinate  in  a  rectangular 
ct^-ordinate  system,  then  this  equation  represents  a  circle.     The 


420  BRAGSTAD:     REPULSION    MOTOR. 

same  goes  through  the  initial  point  of  the  co-ordinates  and  has  the 
radius 


The  co-ordinates  of  the  central  point  are 

x 


Abscissae  w  =  E- 


2  (rrk 
Ordinates  M  «= 


With  constant  terminal  pressure  we  thus  have  the  current  vector 
according  to  strength  and  phase  as  the  distance  from  the  initial 
point  to  a  circle.  By  means  of  this  circle  we  can  follow  the  work 
in  the  motor.  We  will  first  consider  the  number  of  revolutions,  or 

what  is  the  same,  the  relation  — . 

c 

According  to  equation  19a  we  have 


c       sin  a  cos  a  (£  x  -f-  f)  r)        sin  a  coft  a     ^ 
Here  we  have  i?  xk  —  £  rk=  Zj  =  o  a  straight  line  through  the 
initial  point  of  the  co-ordinate  system.    According  to  equation  19, 

\  =  —  with  u  =  o.    The  straight  line  ^==0  thus  goes  through 

^ 

the  short-circuit  point  of  the  motor.    The  short-circuit  current  is 
0  K  in  Fig.  4. 

£  a;  -}-^r  =  L2  =  0is  likewise  a  straight  line,  which  stands 
perpendicularly  on  the  connecting  line  (central  line)  between  the 
origin  of  co-ordinates  and  the  central  point  of  the  circle.  This 
line  is,  therefore,  a  tangent  at  the  initial  point.  Every  vector  is  a 
ray  in  a  group  of  rays,  and  has  the  equation 

u    . 

—  sin  a  cos  a  1^  —  L\  mm  o. 

c 

For  u  =  c  the  equation  of  the  ray  (synchronous  line)  is 
Zs  =  sin  a  cos  a  L%  —  Z>}  =  t)  (r  sin  a  cos  a  —  ak)  +  £  (a  sin  a 
cos  a  -f-  rk  )  =  o. 

For  any  point  P  of  the  circle,  —  is  the  double  relation  between 
the  four  rays  and  the  same  is  cut  off  on  a  transverse  line,  thus 


dc 


BRAVtiTAD:     REPULSION    MOTOR.  421 


If  we  draw  the  transverse  line  parallel  to  the  straight  line 
then  the  double  relation  passes  over  into  the  single  relation  and 
we  get 


c 

We  can,  therefore,  read  on  the  transverse  line  parallel  to  the 
straight  line  L.2—  o  the  speed  of  rotation  for  every  current. 

The  synchronous  line  L3=  o  can  be  constructed  as  follows  : 
Over  the  section  FD  =  z  as  diameter  we  describe  a  circle  and  mark 
off  the  brush  angle  «  =  GDT  in  point  D.  The  synchronous  line 
then  runs  through  point  T.  A  perpendicular  line  from  T  onto  sec- 
tion FD  cuts  the  latter  in  point  G;  OG  is  the  short-circuit  im- 
pedance of  the  motor  with  the  two  components  r*  =  rg  —  r  cos2  a 
and  ajk  =  xg  —  x  cos2  «.  The  short-circuit  line  £±=  o  thus  goes 
through  point  G.  The  short-circuit  point  K  on  the  diagram  circle 

is  an  inverse  point  to  point  G,  in  that  OK  is  proportional  to  -Q-Q  . 

A  modification  of  the  brush  angle  a  changes  the  size  of  the  diagram 
circle  and  the  position  of  the  short-circuit  point  K  as  also  the  posi- 
tion of  the  synchronous  line  £3=0.  If  a  is  made  so  large,  that 
the  synchronous  line  becomes  a  tangent  to  the  circle  over  FDf 
synchronous  speed  occurs  with  the  smallest  phase  displacement. 
When  G  moves  toward  F,  if,  therefore,  a  is  reduced,  the  short- 
circuit  point  K  continually  moves  higher  on  the  circle;  the  losses 
are  thus  increased.  At  the  same  time,  however,  the  diameter  of 
the  diagram  circle  and  therewith  the  maximum  output  of  the  motor 
are  increased.  The  question  as  to  the  most  favorable  brush  dis- 
placement angle  can  thus  be  answered  in  very  many  different  ways 
according  to  the  special  result  which  is  to  be  obtained.  By  means 
of  the  diagram  in  Fig.  4,  we  can  easily  find  the  most  favorable  brush 
position  for  a  given  case. 

We  will  now  see  how  we  can  represent  the  moment  of  rotation 
in  the  diagram.  According  to  equation  IV 

D  =  (—  )    J8  2   (xt  sin  a  cos  a  --  rt  sin2  a)  . 

\  2%  '  *  C  * 

In  accordance  to  the  circle  equation  VI,  we  have  however 


and  according  to  equation  22 

u  —          7  x*  —  *r*  _  L\ 

c       sin  a  cos  a  (£  x  -\~  7  **)       sin  «  cos 


422 


BRAGSTAD:     REPULSION    MOTOR. 


23) 


Introducing  this  for  the  moment  of  rotation  we  get 

D-  (Ji)'L*r,  -^(eL+ji 

\  zt  '       z      *  cos  a  \    \  *       rt 

—  *)    \Xk  --  ~  COS2  a)  j 

\ 

••-'*/ 


sn« 

- 

cos  a 


The  straight  line  $  re  —  y  xe  =  L^=  o  is  the  no-load  line,  the 
construction  of  which  we  have  given  in  Fig.  3. 


M=C 


FIG.  4. 

The  moment  of  rotation  is  at  any  point  proportional  to  tHe  dis- 
tance of  the  same  from  the  no-load  line.  In  short-circuit  the  cur- 
rent is 


(rg  —  r  cos2  a)  2+  (Xg  —  x  cos2  a)2 
The  starting  moment  is,  therefore, 

/  z  \2 
24)  Dk  =  ^— -j    /k2  £Ct  sin  o  cos  a 

(2a\  2    £2  iCt  sin  a  cos  a 
'v  ov^ 


r  coa2  a)2  -f  (xg  —  x  cos2  a)r 


BRAGSTA.D:     REPULSION    MOTOR.  423 

Hereby  the  measure  for  the  determination  of  the  moment  of 
rotation  is  given  by  the  distance  from  the  no-load  line  for  every 
point. 

We  will  now  introduce  the  relation  between  the  moment  of 
rotation  in  watts  relative  to  synchronism  and  the  introduced  watts. 
This  is 


25)  d=   --= 

We    ~          2t  /  2$         COS  a 

At  starting  we  have 


—  sin  a  cos 


It  is  seen  that  *  is  the  double  relation  in  a  group  of  vectors  con- 
sisting of  the  abscissae  axis  (17—0),  the  no-load  line  (L4=o) 
and  the  short-circuit  line  (L^=o).  Because  in  this  group  of 


FIG.  5. 

vectors  the  double  relation  is  given  for  the  short-circuit  line  as 
equal  d  9  the  same  can  be  at  once  determined  for  any  vector  <?. 
If  in  Fig.  5,  Lt=  o  is  the  short-circuit  line  and  L±=  o  the  no-load 
line,  if  further  the  straight  line  ac  is  drawn  parallel  to  the  abscissa^ 
axis,  we  have  for  a  vector  through  the  center  point  P 

_!==£_* 

#k       c  a 
Thus  if  we  make  ca=dtLf  we  have 

t=cb. 
Because  now,  through  the  two  constructions  given  in  Figs.  4  and 

5,  the  values  —  and  3  =  =-can  be  read  off  for  every  point  of  the 


424  BRAGSTAD:     REPULSION    MOTOR. 

diagram  by  carrying  the  current  vector  to  the  respective  point,  we 
have  also  given  us  at  once  for  every  point  the  efficiency  of  the 
motor  ;  for  the  efficiency  is 


We  thus  need  only  multiply  the  two  values  read  off. 

If  the  diagram  is  to  be  constructed  for  a  motor  only  planned,  the 
separate  reactances  and  resistances  can  be  calculated  and  they  need 
only  be  introduced  properly  into  the  given  formula.  Some  abbrevia- 
tions and  omissions  are  then  permissible  not  introduced  here,  on 
account  of  their  general  character. 

If  the  motor  is  already  constructed,  the  diagram  can  be  deter- 
mined by  some  measured  values  and  we  can  tHus  get  at  the  mode  of 
working  of  the  motor  without  the  necessity  of  carrying  out  a  com- 
plete brake  test.  Different  methods  may  be  followed,  of  which  only 
a  few  examples  are  to  be  here  given. 

If  we  measure  at  standstill  the  impedance  between  the  primary 
terminals,  first  with  a  brush  displacement  «  =  o  and  then  with 
a  =90  deg.  (or  what  is  the  same,  with  open  secondary  circuit), 
we  get  the  two  points  F  and  D  in  Fig.  4.  Thereby  we  have  the 
line  L2=  o,  and  for  any  brush  angle  «  the  short-circuit  point  with 
the  short-circuit  line  L-=  o,  the  synchronous  line  Ls=  o,  and 
according  to  the  construction  given  in  Fig.  3  the  no-load  line 
Li=  o  and  the  no-load  point.  The  circle  is  furthermore  de- 
termined in  that  its  center  point  must  lie  on  a  line  parallel 
to  FD  through  the  initial  point.  The  only  feature  lacking  in  order 
to  make  the  diagram  complete  is  the  scale  to  give  us  the  moment 
of  rotation  and  thereby  the  determination  of  the  degree  of  efficiency. 
The  same  can  be  most  simply  obtained  by  measuring  the  torque  D  k 
at  standstill  and  with  any  brush  angle  a.  If  now  we  put  according 
to  equation  26 

**-^  =  ae  (see  Fig.  5) 

where  TF^k    is  the  electric  power  supplied  at  standstill  with  the 
respective  brush  position  «,  then  for  any  brush  position  and  any 

speed  —  ,  for  which  the  power  supplied  is  We,  the  moment  of  rota- 

tion D  —  9  We  =  be  We 
and  the  degree  of  efficiency 

u      D       u          u      . 
'?=  —  *-Ti7~==—  £=—  •  be. 

1      c     We       c  c 


BRAGSTAD:     REPULSION    MOTOR.  425 

For  another  brush  angle  a1  with  the  short-circuit  resistance  r^ 
and  the  section  ate1  between  the  short-circuit  and  no-load  line  we 
have  according  to  equation  26 

dk        rk  sin  a1  cos  a1 

^k1       ^K1  pin  a  cos  a 
We  would  thus  have  to  put  for  this  angle 

TV    sin  a1  cos  a1 

<V=  «  cl  =  -f-  — a  c 

/•^   sin  a  cos  a 

D  =  tl  We  =  bl  c1  We . 

From  this  we  must  determine  the  moment  of  rotation  and  the 
efficiency  for  any  brush  angle  a1,  when  the  moment  of  torque  f 01  an 
angle  «  has  been  determined. 

MAXIMUM  OUTPUT  WITH  CONSTANT  TERMINAL  PRESSUBB. 
In  accordance  with  equations  22  and  23,  we  have 

u  f\  Xk — £?*k          ^2  R    fiXK-Zr* 

C  sin  a  cos  a  (£  x  4~  7  r)          %    sin  a  cos  a  1^* 
22  R      sin  a 


We  thus  have 

2 


cos"  a 
If  we  put 


cos  Pk=—  5 


008        =  —  J   8in 


sm     =  -- 


then  f  k  =  angle  between  short-circuit  line  and  ordinate  axis 
pe  =  angle  between  no-load  line  and  ordinate  axis 
<p   =  phase  displacement  of  the  current 

and  we  have 


The  mechanical  output  is,  therefore,  a  maximum,  when 


or 

29) 


426  BRAGSTAD:     REPULSION    MOTOR. 

The  output  of  the  motor  is  a  maximum,  when  the  phase  displace- 
ment angle  has  the  arithmetical  mean  value  of  the  two-phase  dis- 
placement angles  at  short-circuit  and  at  no-load.  If  we  put  down 
the  short-circuit  line  as 


Zk 

and  the  no-load  line  as 


then  the  equation  of  the  current  vector  at  maximum  output  is 


or 

31)  £  (re  zk  +  rk  ze)  _  ^  (Xe  zk  4. 

We  combine  this  with  the  circle  equation 


and  we  get 

X*  Ze>2  + 
X  (Xe  *k  +  Xk 


^k  -f 

^*,)-fi  ^to»+^ 
We  have 


-x  cos8 
Hence 


/k  2e 

9     and  $  are  watt  and  wattless  current  at  maximum  output.    The 
output  factor  with  this  output  is 


, 


2  +  (re  Zk  +  rk  Ze  ) 

The  number  of  revolutions  with  maximum  output  is  found  as 
follows 


C          su  a  cuS  «       r 


BRAGSTAD:     REPULSION    MOTOR.  427 

e  Zk  +  rk  ge  )  -  ?*k   (Xe  3k 


sin  a  cos  a  [r 

3k     £k  re  - 


sin  a  cos  a  L*k  (rre  -f-  xxe 


sn  a  cos  a 
Now  we  have 


sin  a  cos  a  (rrk  -f-  £#k )      ?*t  c 

where  ue  is  the  number  of  revolutions  at  no-load   (equation  9), 
Thus  we  have  with  maximum  output 

33)  —  =  .- -. 

C         2U  +  3e   C 

The  moment  of  rotation  with  maximum  output  is 
D  =   (^  V  -^-  rt  ^-a  ^  ^e  —  7  *e )     (Equation  23) 


where  for  £  and  ^  we  must  introduce  the  current  component  for 
this  maximum  output.     We  then  have 


2e  )8 


Here  ^  -\-and  /i'  -^-are  the  current  components  when  the  motor 

«k  *  Sk2 

is  at  standstill  and  the  torque  is 

/sa\a27e      sin  a  /        a:k         ,  pr*  \ 
1}*=*  [  — )    rt  ( re  A  — =•  —  xe  &  — «  ] 

\Zt  I        Z  COS  a   \  25k2  2k2  / 

Consequently  the  moment  of  rotation  for  maximum  output  is 


.  x~c     -     ,    ~.     ,)a  +  (^e2k  + 

«4) 

=^k 


e+^k 

The  output  itself  is 


428  BRAGSTAD:     REPULSION    MOTOR. 

We  finally  find  the  efficiency  for  the  maximum  output 

W                         D                       *    3  »    We 
"mmax          -^k  %*    Ze 


86) 

For  the  use  of  the  formula  indicated  in  the  las*t  section  in  con- 
sidering a  motor  design,  it  is  only  necessary  to  make  no-load 
measurements  at  standstill  of  the  impedance  Z^  and  the  torque  Dk 
and  at  no-load,  of  the  impedance  Ze  and  the  number  of  revolu- 
tions ue. 


THEORY  OF  THE  COMPENSATED  REPULSION 

MOTOR. 


BY  ERNST  DANIELSON. 


Of  late  there  has  been  a  great  deal  written  about  the  compen- 
sated repulsion  motor,  which  fairly  may  be  considered  the  most 
modern  type  of  motor  in  the  present  electrical  industry.  Not  only 
analytical  but  also  graphical  methods  have  been  given  for  explain- 
ing its  qualities.  It  appears,  however,  that  a  complete  analytical 
treatment,  considering  the  leakage  —  that  is  to  say,  formulas  for 
the  calculation  of  current,  torque  and  lag  with  known  voltage, 
brush  position  and  speed  —  have  not  as  yet  been  published.  In  this 
paper  the  author  will  present  the  formulas  which  are  used  by  The 
Allmanna  Svenska  Elektriska  Aktiebolaget  of  Westeras,  Sweden, 
for  figuring  such  motors,  and  which  have  given  results  in  good 
agreement  with  actual  tests. 

It  should  be  mentioned  before  entering  into  detail?,  that  in  the 
following  theory  the  magnetic  losses  are  neglected  and  that  accord- 
ingly the  magnetic  vector  is  considered  the  same  as  the  resulting 
ampere-turns.  When  using  the  formulas  given  below,  it  is  there- 
fore necessary,  when  aiming  at  the  utmost  accuracy,  to  apply  a  cor- 
rection for  these  losses. 

Referring  to  Fig.  1,  let  7k  sin  at 

be  the  current  on  short-circuit,  assuming  the  direction  as  the  posi- 
tion when  the  current  is  flowing  in  the  winding  from  c  to  d; 
a  =  ZnN;  (N=  frequency). 

This  current  creates  leaking  lines  of  force,  viz.,  lines  of  force, 
yiz.,  lines  cutting  only  the  rotor  windings: 

=znr  Ik  sin  at 

nr  —  Conductors  round  rotor, 
£  =  Leakage  co-efficient. 

These  lines  of  force  induce  on  short-circuit  an  e.m.f. 
=  _  £  .,,2  jfc  jyr  cog  at  1()-8  yoits. 

The  lines  of  force  in  the  direction  c  d  which  enter  from  the  rotor 
into  the  stator  we  designate, 

=  B.  sin  (at  +  ft) 

[429J 


430 


DANIELSON:     COMPENSATED  REPULSION  MOTOR. 


and  those  which  in  direction  b  a  cut  the  rotor  winding  (sum  of 
leaking  and  useful  lines), 

—  A.  sin  (at  -f-  a). 

In  these  two  last  formulas,  A  and  B  are  the  lines  per  pole,  and 
ft  and  a  the  difference  of  phase  of  these  lines  and  the  current  I  * 
The  lines  B  induce  in  the  short-circuit  an  e.m.f., 

=  —  B  Nnt  cos  (at  -f-  0)   10~8  volts. 

The  lines  A  induce  in  the  same  circuit  on  account  of  the  motion 
(this  assumed  clockwise), 

=  A,  JVi.  ftr'sin  (at  -f-  a).  10"8  volts. 
NI  being  the  speed  (in  frequency).    In  the  last  two  formulas  it  is 


Fm.  1. 

assumed  that  the  rotor  winding  is  either  two-pole  or  series-con- 
nected, so  that    each  conductor  carries  a  current  =_*.     If  now 

2 
r  =  ohmic  resistance  of  short-circuit,  then 

rkr  sin  at  108  =  A.  A\  ?'P  sin  (at  +  a)  —  B  nr  c«  *  (at-{-  fi)  —  f //.J 
This  equation  must  be  valid  for  any  value  on  t,  accordingly, 
7k.  r.  \(P  =  A.  Nv  wrcos«r-f  B   Nr,r*iufi.  (\) 

A.  N^  sin  a  =B.  N'.  cos  /3  +  .-.  n,  r. .  ^V!  (  ) 

In  the  stator  circuit  there  flows  a  curreni,  the  phase  of  which 


DANIELSON:     COMPENSATED  REPULSION  MOTOR.  431 

is  the  same  as  that  of  the  lines  of  force  A,  these  lines  being  caused 
only  by  this  current.    This  current  we  may  represent  by 

7.  sin  (at  +  «). 

The  direction  is  positive  when  the  current  in  the  rotor  winding 
flows  from  b  to  a.  This  current  causes  following  lines  of  force : 

7.  Lines  of  force  cutting  only  the  rotor  windings: 

=  £ .  nT .  I .  sin  (at  -j-a) 
in  direction  b  a. 

II.  Lines  of  force  cutting  both  rotor-  and  stator-winding  in 
direction  b  a: 

=  Z.  I.  sin  (at  -{-  a)  (nr  —  nB .  sin  0) 

C  is  a  co-efficient  depending  on  the  geometrical  form  of  the 
machine  and  the  permeability  of  the  iron;  ng  =  number  of  con- 
ductors on  stator,  the  same  assumption  being  made  as  for  7/r> 

viz.,  that  each  conductor  carries  a  current  =  _  .0  =  angle  of  brush 

2 
position  (see  Fig.  1). 

The  sum  of  these  lines  of  force  must  equal  A.  sin  (at  -{-a). 
Accordingly 

A  =  I.  [:K  —  n. .  Bin  0) +£.  n,  ] 
or  :     A  =  I.  D 
if  :      D  =  C   (nr  —  ns .  sin  0)  -f  £.  nr  . 

The  lines  cutting  both  stator  and  rotor  winding  in  direction  c  d 
are  caused  by  the  combined  influence  of  ampere-turns  in  stator  and 
rotor.  Hence : 

B.  sin  (at  +  0)= 

C  [w, .  I.  sin  (at  +  a),  cos  0  -f-  Tjj .  w, .  sin  a£] . . .     (1) 
This  equation  is  valid  for  any  value  of  the  angle  a  t,  therefore : 

sin  at  (B.  cos  /5 —  C.  w§  I.  cos  0  -  C.  wr  ^k)  =  0 (2) 

cos  at  (B.siap  —  C.  w8  I.  sin  a.  cos  6)  =  0 ...   (3) 

and 

B  cos  ft C.  ??8  I.  cos  a.  cos  0  —  C.  »r     -4—0 (4) 

B.  sin  £  —  C.  ras  Z  sin  a.  cos  0  =  0 (5) 

The  equations  1,  2,  3,  4  and  5  contain,  besides  I,  five  unknown 
quantities  A,  B,  «,  0  and  ^k,  and  hence  give  value?  of  these  ex- 
pressed in  7  and  known  numbers. 

Now  combining  equations  (1)  and  (2),  then  (1)  with  (4),  and 
afterward  eliminating  B  by  means  of  (5)  and  A  by  means  of  (3), 
we  get : 


432  DANIELSON:     COMPENSATED  REPULSION  MOTOR. 

~-j£.  108  —  N.  nr*.  ns.  cos  9  (C  +  £) 


(6) 


r.  w  .  cos 


.  108  +  N^  .  nr  *  .  D  (l  +  1 


"~C./*s.  cos*      yr  r.  los         -      r.  10s     •••• 

These  equations  show  that  a  and  y#  are  independent  of  the 
current. 

From  (4)  and  (5)  we  obtain 

„        C.  ws  Z  sin  a.  cos  0  . 

sin/*         ~  .................   <8' 

,.        wg.  Z  sin  a.  cos  0  ,  . 

Zk  =  -'      —  -  --  (cot  /3—  cot  a)  ......   (9) 

In  the  stator  circuit,  the  induced  e.m.f's.  are: 

/.  In  the  rotor  winding,  by  the  lines  of  force  along  c  d: 

=  —  [£•  nr.  7k.  sin  at  +  B.  sin  (at  +  ft)}.  NI.  n^  10~«. 
//.  In  the  rotor  winding,  by  the  lines  of  force  along  b  a: 

=  —  A.  cos  (at  •+-  a).  N~.  wr.  l<r8. 

HI.  In  the  stator  winding,  by  the  lines  of  force  along  b  a: 
=  C.  /.  cos  (at  +  a)  (nt  —  na.  sin  0).  N.  nB.  sin  0.  lO"8. 

IV.  In  the  stator  winding,  by  the  lines  of  force  along  c  d: 

=  —  B.  cos  (at  -1-  /3).  N.  ws.  cos  0.  ICT8. 

V.  In  the  stator  winding,  by  self-induction: 

=  —  /.  cos  (at  +  a)  n*  X.  N.  10-*. 
A  =  Leakage  co-efficient  corresponding  to  £. 

VI.  Influence  of  ohmic  resistance: 

=  —  /.  sin  (at  -j-  a).  E. 

E  —  total  resistance  of  stator  circuit  (including  rotor  winding, 
brushes,  etc.).  If  now  the  machine  acts  as  a  motor,  then  the  im- 
pressed e.m.f.  must  equal  the  sum  of  above  six  expressions  with 
opposite  signs. 

Accordingly,  if  E  =  voltage  at  terminals  of  motor  (amplitude), 
and  y  its  phase  : 
—  JS'sin  (at  +  y).  108  =  —  -  Z  sin  (at  +  a).  JR.  108. 

—  Z  cos  (at  +  a)  n*.  L  IT—  B.  cos  (at  +  /?).  F.  ns  cos  8 
+  C.  Z  cos  (at  4-  a)  (nr  —  ns.  sin  6).  N.  r*8.  sin  0 

—  A.  cos  (at  -{-  a).  N~.  nr 

—  [£.  wr.  Zk.  sin  at  4-  B.  sin  (at  4-  ft)]  NI.  %  .......   (10) 


DANIELSON:     COMPENSATED  REPULSION  MOTOR.          433 

Now  substituting  for  A,  B  and/k  their  values  [equations  (3), 
(8),  (9)] 

E 

j-.  sin  (at  -{-  y)  =  JR.  sin  (at  -f  or)  -f-  V.  cos  (a£  -}-  or) 

+  W.  cos  (at  +  ft)  4-  tf  sin  (a*  -j-  /3)  +  T7.  sin  a*....  (11) 
in  which 

F  =  [>82.  A..  JV—  C.  N.  nB.  sin  (9  (rcr  —  wg  sin  0)  -f  fr  nt  J)].  10~< 
TF=  C.  ras2.  sin  a.  cos2  9.  JVI  lO"8 
£T  =  C.  ws.  sin  <ar.  cos  0.  ^V^.  wr.  10"8 

T  =   g.Hr.  NI.  Wg.  COS  ^  (cot  ft  -  COt  a).  10"8. 

Developing  the  goniometric  functions  of  the  sums  (at-}-  a)  and 
(at  +  ft)  and  considering  that  the  equation  (11)  is  valid  for  any 
value  of  at  we  get: 

.  .   (12) 


and  tan  ^  =  —  , 

in  which  expressions 

p=  ^.  sin  a:  4-  T7:  cos  a  +  TF.  cot  /?  +  U 

Q=  E.  cos  or  —  V.  sin  a  —  TF+  #  cot  y^  +  T.  sin  a. 

These  equations  give  values  of  current  and  A  when  voltage,  fre- 
quency and  speed  are  known. 

Though  I  and  E  have  been  defined  as  amplitudes  of  current  and 
e.m.f.  the  equation  (12)  of  course  also  holds  good  for  effective 
values. 

The  angle  by  which  the  current  I  is  iri  advance  being  OL  and  yy 
the  angle  by  which  the  terminal  voltage  is  in  advance,  both  relating 
to  the  same  epoch,  then  the  angle  of  lag  of  current  behind  e.m.f.  is 

q)  =  \  —  a. 

CALCULATION  OP  TORQUE. 
I.  Torque  from  lines  of  force  along  a  d  and  current  I,  clockwise  : 

=  B.  sin  (at  -f-  ft).  nr  .  I.  sin  (at  -\-  a),  p.  -f—. 

&7T 

dynes  at  1  cm  radius,  p  —  number  of  pairs  of  poles. 

The  integrated  average  value  during  a  period  calculated  from 
above  expressions  is 

B.  I.  cos  (a  —  ft).  nr.  p.  0.1 

~TF~ 

ELEC.  RYS.  —  28. 


434          DANIELSON:     COMPENSATED  REPULSION  MOTOR. 

II.  Torque  from  lines  of   force  along  la  and  current  I*9  clock- 
wise: 

5=3 —  C.  I.  sin  (at  -f-  a)  (nr  —  7?.  sin  0).  n-I*.  sin  at.  »  — '— 

*  in 
dynes  at  1  cm  radius.    Average  value 

C.  L  (",  —  ras.  sin  0).  nr .  Zk .  cos  a.  p.  0.1 


C.  JTZ.  nt .  sin  a.  cos  a.  cos  9  p 

40.7T 


The  resulting  torque  is  the  sum  of  the  above  expressions.  Sub- 
stituting for  7k  and  B  their  values,  we  obtain: 

nr  (tan  a  -\-  cot  a) 

+  ns  .  sin  6  (cot  fi  —  cot  ex)  -" 
and  expressed  in  kilograms  at  1  meter  radius  with  current  expressed 
in  effective  amperes,  after  some  transformation : 

K=*  1.625 .  10-10  C.  11 .  n%  .  cosd.  p.  [nr  -f  ^^s .  sin  0 
(sin  a.  cos  a.  cot  fi  —  cos2  <*)] 

The  formulas  thus  obtained  suffice  for  figuring  the  behavior  of  a 
motor,  if  its  design  is  given.  The  magnetic  induction  in  the  direc- 
tions 6  a  and  c  d  can  also  be  calculated,  and  accordingly  correc- 
tions can  be  made  for  the  iron  losses. 

Motors  of  this  kind  are  generally  used  for  such  purposes  where 
it  is  necessary  that  they  can  work  in  both  directions.  This  being 
the  case,  it  is  of  advantage  to  arrange  the  machinery  in  such  a  way 
that  no  shifting  of  brushes  is  necessary.  If  8  is  made  =  0,  the 
position  of  the  brushes  is  perfectly  symmetrical  and  accordingly 
allows  the  motor  to  run  in  any  direction.  But  if  0=0,  the 
formulas  are  also  greatly  simplified.  At  the  end  of  the  paper  a 
summary  of  the  formulas  is  given,  not  only  in  their  most  general 
form,  but  also  for  8  =  0. 

MAXIMUM  TORQUE  AT  START. 

Supposing  that  from  the  reasons  just  stated,  we  use  the  arrange- 
ment with  a  symmetrical  brush  position  (0  =  0);  then  it  is  of 
interest  to  investigate  what  relation  nr  should  have  to  ns,  the  latter 
being  given,  in  order  to  get  maximum  starting  torque. 

Accordingly,  a  motor  with  known  ng,  C,  £,  etc.,  is  given;  for 
what  value  of  nr  is  the  maximum  torque  obtained  at  ^=0? 

Substitute  in  the  formulas, 

B  =  0;  N[  =  0;  nr  =  ns .  c  then 


DANIELJ30N:     COMPENSATED  REPULSiON  MOTOR.          435 

eot.-—  ^•"•• 
r.  lu8 


r. 


The  angle   a  (difference  of  phase  of  stator  and  rotor  current) 
ifi  at  starting  a  little  less  than  180  degs.    Accordingly,  we  may  write, 


sn  a  =»= 

cot  a 


^?tT9 

ir=o 

If  we  now  neglect  the  quantities  which  contain  r  and  R,  then, 


n*  \\  4-  cMC  +  *)]  cos  a 


Seeing  now  that  or  is  a  trifle  less  than  180  degs.,  then  cos  a  = 
•+•  —  1  and  sin  a  =  ~  0 
The  denominator,  therefore,  becomes: 


and  the  expression  for  the  torque  is 
" 


X  a  constant 


Differentiating  : 

Jf-  [A+  «'  (c  +  5)  +?i 

(denominator  of  differential  coefficient  omitted,  not  possibly  being 
=  0). 

As  now  the  expressions  in  brackets  could  not  be  =  0  (containing 
cnly  positive  quantities),  then  for  maximum  torque: 

A+  c*  .  (C  +  £)  +       --  4e*(C  +  £)  -0 


—  4/ 


430  DANIEL80N:     COMPENSATED  REPULSION  MOTOR. 

If    A  =  %  and  small  in  comparison  to  C,  then 


For  a  railway  motor,  which  for  mechanical  reasons  cannot  have 
a  very  small  air-gap,  -^  may  come  out  something  like  1/20  which 

corresponds  to  c=  0.183.  Accordingly,  the  number  of  conductors 
on  rotor  should  be  1/5  —  1/6  of  the  number  of  conductors  on  stator. 

At  starting  —  often  may,  on  account  of  saturation  of  iron,  in- 

crease up  to  1/6;  this  would  correspond  to  c  =  0.82VV6—  °-335 
or  the  number  of  rotor  conductors  is  about  one-third  of  the  stator 
conductors. 

MAXIMUM  TORQUE  PER  VOLTAMPERE  AT  START. 

It  may  be  of  still  more  interest  to  investigate  what  relation  n( 
must  have  to  ns  in  order  to  obtain  the  maximum  torque  per  volt- 
ampere  at  start.  That  is  to  say,  if  the  voltage  is  kept  constant, 
the  maximum  torque  per  ampere  at  start.  The  expression  for  this. 
quantity  is  easily  obtained  : 


dd 

For   d  =  maximum  :  —  -  =  0 
d  c 

4)-o 


or  if  £  =  A  and  small  compared  with  Cf 


£  1  £  1 

For   -=~-  then  c=»~  0.57;   For   ~-=  --  - 

then  c=~0.32.  Accordingly,  if  wv  wish  to  obtain  the  greatest 
economy  with  current  at  start,  the  number  of  rotor  conductors  must 
be  chosen  larger  than  if  the  greatest  torque  is  aimed  at. 


DANIELSON:     COMPENSATED  REPULSION  MOTOR. 


437 


It  should  be  pointed  out  that  for  other  reasons  (considerations 
as  to  lag,  etc.),  the  number  of  rotor  conductors  often  must  be  some- 
what modified. 

Finally,  the  results  of  experiments  with  a  motor  of  this  kind 
will  be  given.  The  machine  was  made  by  the  Allmanna  Svenska 
Elektriska  Aktiebolaget,  Westeras,  and  tested  in  their  works. 

The  stator  of  this  experimental  machine  (see  Fig.  2)  had  72 


Stator 


Rotor         • >     11 

Dimensions:  .Millimeter 


PIG.  9. 


half-open  slots,  each  containing  12  conductors  of  2.5  mm  diameter. 
The  winding  was  divided  in  two  groups  which  were  connected  in 
parallel.  The  rotor  had  49  slots  with  6  wires  of  2.8  mm  diameter. 
Winding,  series  drum.  Number  of  poles,  4.  Air-gap,  1  mm.  Fre- 
quency, 27.  Voltage,  200. 

Calculation  of  C. 

A  current  in  the  rotor  winding  =  7  causes  a  flow  of  lines  in  the 
air-gap  (neglecting  iron)  per  pole : 


ft.  £  1.85. -1.  469. 1 
42  0.2  2 


(459=area  of  1  pole). 
Accordingly : 


C=180 


438          DANIELSON:     COMPENSATED  REPULSION  MOTOR. 


Calculation  of  %=\. 

The  constants  of  Holart  (see  Elektrotechnische  Zeitschrift 
No.  46,  1903),  are  used: 

£.  I.nr  =  j.  -^-(20  X  0.93  +  0.4  X30).2 

20  =  length  of  one  conductor  in  iron  in  cms. 

30  =  free  length  of  one  conductor  in  iron  in  cms. 
0.93  =  Hobart's  constant. 
0.4   =  Hobart's  constant. 

The  constants  C  and  Z  obtained  from  actual  measurement  (by 
measuring  voltage  and  primary  current  with  brushes  removed  en- 
tirely in  one  case  and  complete  short-circuit  in  the  other  case)  are: 

C  =  208;  £=7.1. 

Other  constants  are : 

#  =  27;  r  =  0.15;  B  =  0.68;  #  =  200;  ns  =  864;  nr «  294. 

Calculating  from  these   constants  and  with  0  =  0,  the  curves 


^50. 
f*°- 

€ 

1  30> 

I 

18. 
17. 
16. 
13. 
14. 
13. 
12. 

U1 

io,fl 

»•! 

8. 
7. 
6. 

_ 

Cal 

ula 

;ed  (pun 

es 

\ 

Bxjlerii 

len 

* 

. 

\\ 

s 

\ 

S 

\ 

\ 

\\ 

\ 

\\ 

-t- 
-fl-Q 

Cos 

\ 

Sr<?>- 

,^ 

^ 

§ 

"**" 

/ 

Arop 

07 

' 

\ 

\ 
\\ 

\ 

l\ 

£nn 

\ 

\ 

3. 

'» 

^ 

V 

1A 

^v 

^N^^ 

10. 

*o 

^r 

Kgjii 

400 


1200 


600          800         1000 
Revolutions  per  Mln. 

Pro.  8. 

in  full  line  (Fig.  3)  are  obtained.    The  dotted  lines  represent  the 
experimental  values. 


DANIELSON:     COMPENSATED  REPULSION  MOTOR.         439 

APPENDIX. 

SUMMARY  OF  FORMULAS. 
General  Formulas. 

D=  C  (nr  —  wg  sin  0)  -f  £.  nr 


111!  _  jynr*  Wg  cos  0 


OOt  a 


F  =  [n.  A.  ^V—  C  ^/>8  «n  (9  (nr  —  wgsi 

TF  =  C  ws2  sin  or  C082  0  ^  10'8 

CT  =  C  ws  ^in  «  cos  6  N[  nr  .lO"8 

T   =gnt  N!  nB  cos  a  (cot  fl—  cot  a)  .lO"8 

P    =  72.  sin  or  +    T7!  cos  or  +    TK  cot  y5  -f   U 

Q   =  72.  cos  a  —  Fsin  a  —  TF  +   PI  cot  /?  +  Tsin  a 


WB  Je  sin  or.  cos  a  (cot  fi  --  cot  or) 

7*-  ~^r 

^T  =  1.625    10-10.  C  7e2.  »>•  cos  0.  p  [nt  + 

7*8  sin  0  (sin  or.  cos  a  cot  /?  —  cosa«)] 

Special  Formulas. 

for  <9  =  0. 


.  108 


7>.  ^i  f  1         5.  wr2  .  cot  a\       Nrt^ 

cot/?=:T^L^-        r.  10'     J  ~  ~7Tu 

F  =  [w.  2  A  JV^  +  JV"wr  J9].  10-8 

TT  =  C.  rtg  2  sin  a  N.  1Q-8 

£T  =  C  '/'g    sin  or.  JV^  nr  .  10~8 

T  =  g  rtt  NI  /'s  (cot  /3  —  cot  a).  10"8 

P  =  R.  bin  a  +  Fcos  a  +  TF  cot  ft  -f  IT 


440          DANIELSON:     COMPENSATED  REPULSION  MOTOR. 

Q     «.  JK.  cos  a  —  Fsin  a—  TF  +  C^cot  /?  +  Tsin  a. 


/e       = 

j-        _  ns  Ie .  sin  a  (cot  ft  —  cot  a) 

K     =  1.625.  10~10  C.  I^n^p  n, 

Notation. 

D  =  SL  coefficient. 

nr  =  number  of  conductors  round  rotor,  provided  the  winding 
is  such  that  each  conductor  carries  half  of  current  on  short-circuit. 
If  the  rotor  has  a  six-pole  parallel  winding,  then  nr  =  active  con- 
ductors divided  by  three. 

nB  *=  number  of  conductors  on  stator,  provided  that  each  con- 
ductor carries  half  of  total  current. 

C=  coefficient  of  magnetization;  C  na  =  number  of  lines  of 
force  per  pole  at  one  ampere  in  stator  circuit,  with  no  current  in 
rotor. 

g  =  coefficient  of  leakage;  £ nr  =  leaking  lines  per  pole  at  one 
ampere  on  short-circuit. 

A  =  leaking  cofficient  for  stator. 

6  =  angle  of  brush  position. 

a  =  angle  of  lag  between  current  in  stator  circuit  and  short- 
circuit. 

ft  =  angle  of  lag  between  lines  of  force  along  b  c  and  short- 
circuited  current. 

N  =  frequency. 

Nl  =  speed    expressed    in    frequency    (at    synchronous    speed 

*,-.»). 

r  =  resistance  of  rotor  circuit  including  short-circuit. 
R    =  resistance  of  short-circuit  including  rotor  winding. 
V.  W,  U,  T,  P  and  Q  =  coefficients. 
/ e  =  stator  current  (effective  value). 
/ek  =  short-circuited  current  (effective  value). 
Ee  =  impressed  e.m.f.  (effective  value). 
K  =  torque  in  kilograms  at  1  meter  radius. 


INDEX  OF  SUBJECTS. 


ACCELERATION,   80,   136. 

maximum   efficiency  with  vari- 
ous methods  of  control,  139. 
power  required,  81. 
used  by  various  classes  of  rail- 
ways, 116. 
used     on     Valtellina     railway, 

167. 

Air,  compressed,  use  of,  155. 
compressors,   155. 

Arnold   system,   design   of, 

35. 
gap  of  motors  of  various  makes, 

126. 

resistance,   81. 
Alternating   current   motors.      (See 

Motors. ) 

railways.      (See  Railways.) 
Armature    reaction,    124. 
BALANCING   transformers,    105. 
Batteries,  storage,  275. 

a.  c.  railways,    163. 

automatic,    280. 

buffer,    parallel    connected, 

263. 

carbon    regulator,    284. 
depreciation,  278. 
distant  from  power  house, 

280. 

efficiency,  163. 
investment,  276. 
maintenance,  278. 
operation   economy,  276. 
plates,    construction,    285. 
plates,  life  of,  285. 
plates,  troubles,  285. 
reasons  for  installing,  276. 
reliability,  278. 
reserve,  278. 
Boosters,  262. 

calculation  of,  264. 
connections,  273. 
design  of,  265. 
efficiency,  286. 
excitation,  automatic,  281. 
excitation,  regulation,  282. 
fly- wheels,  269. 
slip,  267. 


Bow  trolley.      (See  Distribution.) 
Brake,  d.  c.   series  motor,  used  as, 
144. 

equipment,  operation,  200. 
shoes,  character  of,  320. 

friction,  ratio  to  pressure, 

317. 

pressures,  317,  322. 
three-phase     motor,     used     as, 

144. 

Braking,  brake  shoes,  character  of, 
320. 

emergency  application,  319. 
experiments,  321. 
high-speed  trains,  315. 
service  application,  319. 
shortest   stops   on   record,    322. 
British   electric   railways,   52. 
Buffer  -battery,  263. 

machine,  264. 

CABLES,    capacity    distribution    in, 
241. 

grounds   in,   239. 

insulation,  239. 

protection     from      electrolysis, 

310. 
Capacity,     distribution     in     cables, 

241. 

Carbon  regulator,  284. 
Catenary  construction,   160. 
Central    stations,    163. 
Characteristic    curves    of    different 

types   of   motors,    373. 
Circuit  breakers,  oil,  249. 
City  railways.      (See  Railways.) 
Collectors,   current.    (See   Distribu- 
tion. ) 

current,    155. 

Compensated     motors.        (See    Mo- 
tors.) 

Compressors,  air,  motor  driven,  155. 
Conduit  system,  first,  7. 
Contact  shoe  for  third  rail.      (See 

Collectors. ) 

Continuous    current   motors.      (See 
Motors. ) 


(441) 


442 


INDEX  OF  SUBJECTS. 


Control    by    brush    shifting,    151. 
of  large  motors,  217. 
methods,  151. 
multiple  unit,  152,  228. 
first,  17. 
limit  of  number  of  units, 

317. 

potential  regulators,   151. 
rheostatic,     of     induction     mo- 
tors,  133. 

rheostatic,  series  parallel,    151. 
series-parallel,  first,  4. 
of    storage    batteries,    280. 
Ward   Leonard    system,    107. 
Controllers,  cylindrical,    152. 
d.  c.,  weight  of,   154. 
magnetic  blow-out,  first,  13. 
single-phase,   weight  of,    154. 
three-phase,    weight    of,    154. 
weight    of    various   kinds,    152. 
Converter  car,    198. 

car  operation,  201. 
Converters,   synchronous,  252. 
efficiency,    253,    258. 
efficiency   all    day,    259'. 
first   cost,   257,   258. 
frequency,  254. 
hunting,  254. 
inverted,  speed  limiting  devices, 

255. 

overload    capacity,    164. 
power    factor,    control    of,    253. 
protection  of,  250. 
starting  of,  253. 
voltage,  d.  c.,  253. 
Cooling  of  motors,  134. 
Cost  a.  c.  railways  vs.  d.  c.,  166. 
Coupling,  elastic,   148. 

rigid,    148. 
Crank    and    connecting    rod,    motor 

drive,  149. 

Current  collection.      (See  Distribu- 
tion.) 

collectors.      (See  Distribution.) 
collectors,   155. 

Curves,  railway,  minimum,  78. 
Deri  motor,  387. 
Dimensions    of    motors    of    various 

makes,    126. 

Direct    current   motors.       (See   Mo- 
tors.) 
Distribution,  a.  c.,  choice  of  phase, 

174. 

a.  c.,  polyphase,  disadvantages, 
174. 

protection  of  systems,  238. 
cables,  capacity  of,  241. 
collector    current,    high    speed, 
158. 
ideal    current,    162. 


Distribution  —  Continued: 
current  collectors,   155. 
drop,   total   in   trolley,   236. 
fourth  rail,  62. 
overhead    conductors,    59. 

double    trolley,    first,    9. 

first,  4. 

limitation   of,    161. 

lines    connected    to    under- 
ground   lines,   248. 

work  details,    34. 
rail,  return   insulation  of,  312. 

losses  in,  224,  225. 
return      feeder,      practice      in 

United   States,  288. 
third  rail,   62,  160. 

composition  of,   192. 

construction,   192. 

installation  of,   161. 

pressure  of  shoe  open,  200. 

protected  operation,  197. 

protection,    161,   193. 
third  rail  shoe,   193. 

construction,   195. 

current  capacity,  160,  200. 

operation,  199. 

pressure,   200. 
three-phase,  capacity  in,  242. 

inductive  ground,  242. 
total  drop  in  trolley,  236. 
trolleys,  155. 

bow,    64. 

bow,  rolling,  64. 

bow  sliding,  64,   157. 

conductors,     conditions     to 
be  fulfilled  by,  61. 

d.  c.,  voltage,  166. 

drop  in  line,  236. 

high  speed,  "158. 

insulator,    special,   34. 

Oerlikon,    158. 

overhead,  first,  4. 

pressure  on  wire,  64,   158. 

roller,  159. 

shoe,  157. 

suspension     and     distribu- 
tion, 161. 

suspension    catenary,     160. 

switches,  162, 

voltage,  165,   187. 

voltage,    high,    danger    of, 
210. 

voltage,   safe,   209. 

wheel,  157. 

whip,  63,  158. 

wind     pressure     compensa- 
tion, 158. 

wire,  double,  first,  9. 

wire,  ice  and  sleet,  162. 


INDEX  OF  SUBJECTS. 


443 


Distribution  —  Continued: 
two  voltages,   161. 
underground,     protection     from 

electrolysis,  308. 
EFFICIENCY    of    motors    of    various 

makes,    126. 
Electrification    of    steam    railways. 

(See  Railways.) 
Electrolysis,  288. 

a.  c.   system,  210. 

bonding   as  .a   remedy,    313. 

importance  of,  220. 

in  Europe,   311. 

opinions  of  experts,  289. 

ordinances,  288. 

rail   return,   insulation  of,  312. 

return   feeders   used   in   United 

States,  288. 
summary,  data,  289-. 
tables    of    classified    data,    292, 

307. 
E.  m.  f.  of  motors  of  various  makes, 

126. 

Electro-pneumatic    system    of    trac- 
tion, 26. 
Energy,  restoration  of,  218. 

return  to  line,  methods  of,  144. 
Equipment,     railway.       (See     Rail- 
ways. ) 

FIELD    amp.    turns    ratio    to    arma- 
ture  amp.    turns    in    single-phase 
commutator  motor,  13. 
Fly-wheels,  speed  limit,  269. 
Fourth  rail,  62. 

Frequency   best   adapted   to    single- 
phase  railways,  99. 

choice  of,  183,  184. 
GEARING,  double,    148. 
motor,  148. 
single,    148. 

Gearless  motors    first,  15. 
Gear    ratio    of    motors    of    various 

makes,  126. 
Generators,  compounded,  164. 

grounding  of  the  neutral,  242. 
high  speed  fly-wheel,  164. 
polyphase,  self-exciting,  397. 

vs.  single-phase,  231. 
protection  of,  250. 
railway,  capacity  of,  163. 
single-phase  vs.  polyphase,  231. 

self-exciting,   397. 
speed,   drop  with  load,   164. 
Ground  detectors,  247. 
Grounds,    239. 
HEILMAN,  locomotive,  216. 
History  of  electric  railways,   1. 
Hunting  of  synchronous  converters, 

254. 
ICE  and  sleet,   162. 


Impedance,  mutual  inductive,  336. 

self-inductive,  326. 
Induction    motors.      (See    Motors.) 

regulator,    104. 
Insulation  in  cables,  239. 
Insulator,   35. 

trolley,  special,  34. 
Insurance,   236. 

Interurban    railways.       (See    Rail- 
ways. ) 

LINE    construction,    155. 
Line   construction.      (See  .Distribu- 
tion.) 

Liquid,  rehostat,  151,  152. 
construction  of,   142. 
Locomotive,  electric,  106. 
Finzi  type,  168. 
gearless  motors,  first,  15. 
heavy,   177. 
high  voltage,  158. 
Oerlikon  system,  217. 
steam,    freight    draw-bar    pull, 
71. 

power  of,  71. 
weight    per   h.    p.    of   electrical 

equipment,  176. 
London  railways,  68. 
Losses,   distribution,    losses    in   rail 

return,  224,  225. 
MAGNETIC   blow-out,  first,   13. 
Monorail     railways.         (See     Rail- 
ways. ) 

Motor-gearing,  148. 
Motor-generators,  252,  256. 
efficiency,  258. 
efficiency  all  day,  259. 
first  cost,   257,  298. 
starting  of,   256. 
voltage,    257. 
Motors,  acceleration,  136. 
a.  c.,  323. 

classification  of,  60. 
field  of  application,  185. 
on  d.  c.  service,  105. 
vs.  d.  c.,  98,  205. 
characteristic  curves  of  differ- 
ent types,  93,  118,  373. 
control  of.      (See  Control.) 
controllers.      (See  Controllers.) 
cooling  of,   134. 
crank  connection,  149. 
direct  connected,  148. 
d.  c.  advantages,   129. 
data,   126. 
efficiency  of,  129. 
limitations  of,   60,   101. 
losses  in,  133. 
losses   when   starting,   138. 


444 


IXDEX  OF  SUBJECTS. 


Motors,  d.  c. —  Continued: 
series,  air  gap,  119. 

arranged  to  return  energy 
to   line,   144. 

characteristics,  94,  140. 

speed,    characteristic,    140. 

used  as  brake,  144. 
shunt,  equalization  of,  147. 

speed  characteristics,  140. 
d.  c.  sparking,  121. 

starting  torque,   137. 

voltage,    166. 
gearless,    149. 

first,   15. 
induction,  air  gap,  119. 

efficiency    all   day,  259. 

high  voltage,  120. 
polyphase,  225,  330. 

advantages,   173. 

characteristics   of,   93. 
variable     speed,     unity     power 

factor,  397. 

induction,      single-phase,      113, 
335. 

advantages,  173. 

condenser,  339. 

torque,  pulsating,  173. 
induction,    three-phase,    advan- 
tages, 213. 

braking,  quality  of,  144. 

concatenated,      losses      in, 
133. 

concatenation  of,   141. 

data,  127. 

efficiency  of,  129. 

field    of    application,     166, 
181. 

losses  in,  133. 

losses  when  starting,  138. 

mountain  railways,   145. 

power   factor,   132. 

power  factor,  high,  131. 

regulation  of,  132. 

in  secondary,  141. 

rheostatic     control,     losses 
in,   133. 

speed   characteristic,    140. 

speed  variation,  141. 

torque,   170. 

torque  curve,  181. 

torque  starting,   136. 

variable  pole,  143. 
induction,  torque,  172. 
losses,  133. 

at  starting,   138. 
N.  Y.  C.  R.  R.,   131. 
New  York  subway,  134. 
parent,  models  of,   11. 
repulsion,    104,    367,    381,    399. 


Motors  —  Continued: 

repulsion,      compensated,      123, 
388. 

formulas,       summary       of. 
439. 

Lahmeyer,   168. 

rotor,  125. 

slots,  design,  437. 

stator,  124. 

theory  of,  429. 

torque,  calculation,  433. 

torque,   starting,   434,  436. 
repulsion.  Deri,  characteristics, 

387. 

repulsion,      disadvantages      of, 
408. 

performance,  414. 

principal  equation,  410. 

regulation  by  brush  shift- 
ing, 168. 

theory  and  operation,  410. 
reversal  of,  140. 
series,  polyphase,  347. 
series,    single-phase,    112,    350, 
354,  377,  396. 

advantages   of,   103. 

air  gap,  120,  171. 

as  generators,   146. 

characteristics   of,    130. 

comihutation,  perfect,  400. 
series,      single-phase,      compen- 
sated, 359,  399. 

conductively,  360. 

disadvantages  of,  408. 

inductively,  364. 

losses   in,    133. 

winding,   169. 
series    single-phase,    data,    128. 

early  experiments,  102. 

efficiency  of,  129. 

Finzi,  168. 

frame,   120. 

frequency,  99,   131. 

losses  when   starting,    138. 

magnetizing    current,    171. 

power  factor,  131. 

power  at  start,  171,  211. 

railway,  402. 

ratio,  field  amp.  turns  to 
armature  amp.  turns, 
131. 

sparking,  122. 

speed,  characteristic,  104, 
140. 

starting  torque,   136. 

straight,  losses  in,  133. 

torque,  170. 

torque  starting,  171. 
shunt,  polyphase,  341. 
single-phase,  376. 


S.  OF 


445 


Motor-starters,   151. 
liquid,  152. 
starting  torque,  130. 
synchronous,  324. 
Winter-Eichberg,  403. 

characteristics,  403. 
Winter-Eichberg-Latour,  352. 
Multiple   unit   control.       (See  Con- 
trol.) 

Neutralj  grounding  of,  245. 
N.  Y.  C.  R.  R.  locomotive  motors, 

131. 
New  York  subway  motors  used  by, 

134. 
OERLIKON   locomotive,   217. 

trolley,  63. 
Operation     of     Arnold     system     of 

electric  railways,  38. 
Overhead   conductor.       (See   Distri- 
bution. ) 

distribution.        (See     Distribu- 
tion). 

work.      (See  Distribution.) 
Overload  relays,  249. 
POLYPHASE  motors.      (See  Motors.) 
Potential   regulators,   151. 
Power,  cost  factor,  203. 

developed  by  motors  of  various 

makes,  126. 
plant  equipment,  195. 
used  to  operate  various  classes 

of  railways,  116. 

Protection  of  a/c.  distribution  sys- 
tems, 238. 

Pressure  against  trolley  wire,  64. 
Rails,  a.  c.,  resistance,  156. 

insulation  of,   312. 
Railways,  braking,  315. 

British,  capitalization  of,  52. 

mileage  of,  52. 
city,  condition  of   service,   180. 

requirements  of,  95. 
data         concerning         various 

classes,   116. 
dividing    line    between     steam 

and  electric,  87. 
electric,      acceleration,      maxi- 
mum efficiency,  139. 
advantages  of,  65,  85. 
a.  c..  92. 
electric  a.  c.  extension  of  d.  c., 

179. 

extensions  of   d.  c.,   condi- 
tions of,  168. 
rail  loss,  224,  225. 
single-phase,   112. 
three-phase,   112. 
vs.  d.  c.,  Ill,  206. 
electric,  Arnold  system,  26. 
air-compressor.  35. 


Railways,  electric  Arnold  system  — 
Continued : 

car    motor    equipment,    35. 

detailed  description  of,  34. 

operation  of,  38. 

valves,   description   of,   43. 
electric,   British,   52. 

expenses,  53. 

freight   carried,   53. 

passengers  carried,   53. 
electric,  conditions  in  1887,  11. 

conduit  system,   first,  7. 

control  systems.    (See  Con- 
trol. ) 

control  systems,  data,  154. 

cost  a.  c.  vs.  d.  c.,  166. 

current     collection.        ( See 
Distribution.) 

current  collection,   155. 
electric,  d.  c.,   111. 

a.  c.  transmission,   112. 

constant    current,    114. 

limitations  of,    101. 

three- wire,    111. 

two- wire.    111. 

voltage,  166. 
electric,  first,    1. 

first  in  U.  S.,  5. 

heavy  service,  first,  83. 

high-tension    a.     c.     trans- 
mission, first,  16. 

history  of,   1. 

interurban,   first,   16. 

in    various    civilized    coun- 
tries, 19. 

line,    construction,    155. 

power    lost    in    motors    of 
various  types,   133. 

problem  principal,  89. 

requirements  of,  59. 

single-phase,     Arnold     sys- 
tem, 21. 

single-phase,   Spindlerfelde, 
167. 

single-phase       vs.       three- 
phase,   221.   222. 

storage  battery,   114. 

suburban.       traffic      condi- 
tions,  55. 

three-phase,   field   for,   166. 

three-phase       vs.       single- 
phase,  221,  222. 

traffic,   class   of,   53. 

transmission,     three-phase, 
power-factor,  163. 

trunk  line,  ideal,  86. 

vs.  steam,  65. 

Ward,  Leonard,  113. 

wear  and  tear  of,  65. 

weicrht   of  a.   c.   vs.   d.   e., 
186. 


446 


INDEX  OF  SUBJECTS. 


Railways,    electric  —  Continued  : 

weight  per  h.  p.  of  electric 
equipment  on  locomotive, 
176. 
with  converter  substations, 

first,  23. 

elevated,  data,   116. 
high-speed,  79. 
energy,   restoration  of,   218. 
entering  London,  68. 
high-speed,  78. 
industrial,  data,  116. 
journeys    per   head    of    popula- 
tion, 58. 
monorail,  71. 

acceleration  at  start,  80. 
advantages  of    76. 
center  of  gravity  of  car,  80. 
high-speed,    79. 
Manchester  and  Liverpool, 

80. 

minimum  curve,  78. 
safety  of,  79. 
mountain,  data,  116. 
motors  for,  145. 
requirements  of,  98. 
protection  of  system,  238. 
steam,       British,       electrifica- 
tion of,  67. 

capitalization  of,  70. 

cost  of  moving  freight,  71. 

electrification,      effect      on 

mileage,   54. 
electricfication  of,  83. 
electricfication,   results    of, 

54. 

fixed  charges,  71. 
fuel  cost,  71. 

power    of    locomotives, .  71. 
vs.  electric,  65,  87. 
wear  and  tear  of,  65. 
street,  data,  116. 
suburban,   requirements  of,   90. 
suburban,  traffic  conditions,  55. 
surface,  classification,   180. 
telephones,  disturbances  in,  232. 
tractive  effort,  223. 
trunk,  freight,  requirements  of, 

9«. 

trunk  line,  data,   116. 
trunk  line,  ideal,  86. 
trunk,  passenger,   requirements 

of,    97. 

underground,   data,   116. 
Ward-Leonard    system,    214. 

single-phase,    system,    176. 
weight  of  a.  c.  vs.  d.  c.,  186. 
weight   per   h.    p.    of   electrical 
equipment  on  locomotive,  176. 


Relays,  overload,  249.' 
Repulsion  motors.      (See  Motors.) 
Resistance,  a.  c.,  of  rails,  156. 
Restoration  of  energy,   144,  218. 
Return  circuit  losses,  224,  225. 
Rheostat,  liquid,   151,   152. 
construction  of,   142. 
Rotary    converters.       (See    Convert- 
ers,   synchronous. ) 
SERIES  motors.      (See  Motors.) 
Series  parallel  control,  151. 
Service,     classification     of     electric 

railways,    180. 

Shoe,  third  rail.    ( See  Distribution. ) 
Shunt  motors.      (See  Motors.) 
Single-phase    railways.      (See   Rail- 
ways. ) 

Skin  effect,  156. 
Sleet  and  ice,   162. 
.Slip  relation  to  centrifugal  masses, 

267. 
Speed  limiting  devices,  255. 

of    motors    of    various    makes, 

126. 
on  various  classes  of  railwavs, 

116. 
Spindlerfelde    single-phase    railway, 

167. 

Starters,   151. 
Starting  torque,   136. 
Stops,    shortest,   on   record,   322. 
Storage  batteries.      (See  Batteries.) 
mounted    on     motor    cars, 

114. 
Substations,    163. 

distribution   of,    165. 
portable,    197. 

operation,  201. 
protection  of,  250. 
Switches,  overhead,   162. 
Synchronous  converters.      (See  Con- 
verters, synchronous.) 
TELEPHONE,  disturbances  in,  232. 
Third  rail.      (See  Distribution.) 
Track  construction,   192. 
Traction.      (See  Railways.) 
data,   116. 

electric.      (See   Railways.) 
Tractive  effort,  «tio   of,  to  weight 

on  wheels,  66. 
Traffic,  classification  of,  53. 

conditions    of    surburban    rail- 
ways, 55. 

journeys    per    head    of    popula- 
tion  in  larger  cities.  58. 
Train  resistance,  air  pressure,  81. 
Transformers,  balancing,    105. 
railway,  capacity  of,  163. 
regulating,  151. 
regulating,  losses  in,  144. 


IXDEX  OF  SUBJECTS. 


447 


Transformers  —  Continued: 

three-phase-two-phase,      balanc- 
ing of,    175. 
Transmission,  a.  c.,  196. 

a.   c.   wiring  formulas,   234. 
of  power,  first,  6. 
protection  of  system,  238. 
single-phase,    178. 
railways,  230. 
railways,    maximum    econ- 
omy,  233. 

railway,  mechanical  consid- 
erations, 236. 

railway,  voltage  drop,  235. 

vs.  polyphase,  174. 

single-phase  vs.  polyphase,  174. 

telephone,   disturbances  in,  232. 

three-phase,    power     factor    of, 

163. 

voltage,   165. 

Trolley.      (See  Distribution.) 
VALTELLIXA         railway         gearless 
motors,   149. 

acceleration   used,    167. 


Valtellina  railway  gearless  motors 

—  Continued: 
locomotive,  135,  150. 
WARD-LEONARD    system    of    electric 
traction,  107,  113,  176,  216. 
field  of  application,  216. 
Weight  of  motors  of  various  makes, 

126. 

Whip  trolley.      ( See  Distribution. ) 
Wilkesbarre  and  Hazelton  railway, 

189. 
brake       equipment      operation, 

200. 

construction,   192. 
converter  car  operation,  201. 
description  of  road  and  equip- 
ment,   191. 

power  plant  equipment,   195. 
profile,  191. 

third  rail,  composition  of,  192. 
third     rail     shoe     construction, 

195. 

track   construction,    192. 
Wind  pressure  on  trolley,  158. 
Wiring  formulas,  a.  c.,  234. 


UNIVERSITY  OF  CALIFORNIA  LIBRARY 
BERKELEY 

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This  book  is  DUE  on  the  last  date  stamped  below. 


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